Roger was probably the most complete player we have seen in my years. Great serve, moves really well and was always willing to come in [to net]. His forehand, well, there are so many things he can do with that shot. Just an all-around great player with a phenomenal, all-court game. -- Pete Sampras

Federer was only 19 when he seized his 2001 fourth-round Wimbledon upset against seven-time champ Pete Sampras to signal the beginning of the passing of the torch between the two men. Sampras hadn't lost at the All England Club in five years. Federer went on to cement his claim for best male player ever by passing Sampras' record of 14 Grand Slam wins. The Swiss star now owns 17 majors and has held the world No. 1 ranking for 302 weeks, another record for the Open era.

Tremendous foot speed. Probably the best mover with the best footwork of that generation. She handled pressure really well in big matches. And that forehand. Bud Collins called her Fraulein Forehand for a reason. That was a huge weapon for her. The serve was solid, and she had a reliable backhand, but her movement is what put her over the top. -- Chris Evert

Even if Graf didn't have the edge of 22 Grand Slam titles to Serena Williams' 21, Graf's calendar-year sweep of the four Grand Slams and the Olympics in 1988 is something that separates her from Williams. But Serena -- who did win all four majors in a row, just not in the same year -- is breathing down her neck.

She doesn't just have power in her game -- she has blow-you-off-the-court power. Serena has the best serve in the history of the game, for power and placement. But maybe her best asset is her competitiveness. When she was playing her best, there was an absolutely insatiable appetite for winning. -- Chris Evert

Richard Williams said when Serena and Venus were teenagers that Serena, though younger, would turn out to be the better player between his two daughters. Serena's first Grand Slam win against Venus at the 2002 French Open -- her first win in four matches against Venus at a major -- launched her on the path to 20 more major titles and a 16-11 head-to-head mark over Venus. Serena now trails only Graf and Margaret Court's all-time record of 24. She and Venus still dislike playing each other.

Martina set a whole new level for physical fitness and power. I think of athleticism. She had tremendous feel on her volleys. She had strong wrists, so she could maneuver volleys anywhere she wanted. She was the epitome of an all-court player -- more than anyone who came up in that era. -- Chris Evert

Navratilova's decision to defect from communist-run Czechoslovakia in 1975 at the age 18 was the defining moment of her career. She didn't feel she'd reach her potential if she stayed behind the Iron Curtain and allowed the Czech Federation to decide where and when she could play. Once in the U.S., Navratilova whipped herself into top shape and put together nearly invincible seasons of 90-3, 86-1, 78-2 and 89-3 from 1982 to '86. She finished with 18 Grand Slam singles titles, same as her great rival, Chris Evert. Navratilova's 167 singles titles and 177 doubles titles are both records.

He was a sensational player. He even got better after he turned pro. For about the first three or four months, he struggled with the second serve. He worked on getting that a lot better and won his second season Grand Slam after that. Awfully talented guy, really tough to play over five sets. Didn't have a huge serve, but being left-handed helped him in that regard. He won the Slam twice, and I don't think any other man will ever do it once. -- Roy Emerson

Laver straddled the move from the amateur to the Open (or professional) eras of tennis. Although Laver's 200 singles titles are the most in tennis history, it was his ability to pull off a second calendar-year sweep of all four Grand Slam tournaments in 1969 -- seven years after his first Slam sweep! -- that forever underscored his greatness.

He's the best, most efficient player in terms of not allowing the pressure of the perceived consequence to impact his ability to achieve his goal. Pressure doesn't detract from his ability to achieve that goal. Arguably the best second serve I've ever seen. Hitting spots, first and second serve, when the most pressure was on. Nobody better. -- Paul Annacone

Sampras' 2000 victory at Wimbledon arguably established him as the greatest male player of all time (until Roger Federer eclipsed him). Sampras dominated in an era when power serves were becoming the norm. What also separated him was his ability to play a chip-and-charge game and his athleticism (he loved to show off his hops on overhead smashes). Sampras was never as great from the baseline as Andre Agassi was, but he didn't need to be.

He never, never missed. You always had to play very steady against Bjorn. You had to win the match; it would never be given you. I think he was ahead of his time, extremely fit and quick. -- Ivan Lendl

Borg was a teenage prodigy who played Davis Cup at 15 and was barely 18 when he won his first French Open. But being ranked No. 1 wore greatly on him. Borg's career-defining moment came when John McEnroe passed the Swedish star for the No. 1 ranking by defeating him at the 1981 US Open. Borg made himself the biggest "What if?" in men's tennis history by skipping the postmatch news conference and leaving the stadium without showering, taking a car directly to JFK Airport and leaving town. He retired for the first time a few months later, with 11 Slam titles. He was only 26.

Man, he has impressed me the last few years. He's had some of the best results in the history of the game. Look at the competition; he's beaten two of the greatest players ever. It reminds me of what Federer was doing when he dominated. The main thing is he moves better than anyone else. You can't teach that kind of movement and flexibility. Greatest return of serve in the history of the game -- just ahead of Agassi. It's just about impossible to get it by him. -- Pete Sampras

Djokovic's victory over Federer in the 2014 Wimbledon final made him -- not Rafael Nadal -- the first man to defeat Federer at all four Grand Slams. Djokovic has also eclipsed the rapidly fading Nadal as the active player with the best chance to eclipse Federer for best ever, even if he has far to go in the major title tally (12 to Federer's 17). It doesn't hurt that Djokovic has a slight advantage in head-to-head matches against both Federer (23-22) and Nadal (25-23).

I watched him play in Australia. I was amazed at his energy and presence. He makes his opponents feel that. One of the biggest forehands in the game. Probably, mentally the strongest player out there, always a positive attitude when he's on the court. He never, ever stops running. He's a pit bull, always coming after you, chewing on your leg and never letting go. -- Pete Sampras

When Nadal defeated Roger Federer in 2008 at Federer's beloved Wimbledon in one of the greatest matches ever played -- it took 4 hours, 48 minutes to complete between rain delays -- Nadal proved he was more than a clay-court wonder. That match gave him Slam defeats of Federer on hard courts and grass. Nadal's career 23-11 record against Federer has also created a perplexing question: How can Federer be considered the greatest ever when his results are so lopsided versus Nadal?

The toughest player mentally. You never knew what she was thinking or what strategy she was going to choose. -- Martina Navratilova

As a teenager, Evert proved her upset of 24-time Slam winner Margaret Court in 1970 was no fluke when she tore to the 1971 US Open finals opposite Billie Jean King at age 16 to become an overnight sensation. The newspapers called Evert "Chris America," and King proclaimed "She's the one!" who would replace her atop women's tennis and take it to new heights.

He has been one of the greatest players in the history of the game. A very gifted, talented genius -- but with a temper, which had benefits at times and maybe not at times. He was a guy you wanted to watch. Even today, I enjoy watching him play. -- Stefan Edberg

Adjectives don't do McEnroe justice. To describe him as boisterous, combative, fiery and controversial would be a start. McEnroe was known for his rivalries with Bjorn Borg and Jimmy Connors, and his loss to Borg in a fifth-set tiebreaker at the 1980 Wimbledon final is one of the most famed matches in history. He defeated Borg in the finals of the 1980 US Open and Wimbledon in 1981. McEnroe went 6-3 against Connors in Grand Slam events, and they split two meetings in the Wimbledon finals. McEnroe holds the men's record with 149 tournament wins in the Open era: 77 in singles and 72 in doubles.

Very tough to play against, a top competitor. You just have to be on top of your game. I always had trouble with left-handers. I was always very wary of them. He always presented a lot of issues. -- Ivan Lendl

Connors surged to the top of the tennis world in 1974, when he won the first three Grand Slam events of his career at the Australian Open, Wimbledon and US Open. He was barred from competing at the French Open for signing a contract with the World Team Tennis circuit, which cost him a chance at the Grand Slam. However, he embarked on a streak of 160 weeks as the No. 1 player in the world -- a mark that stood as a record until Roger Federer eclipsed it nearly three decades later. Connors still holds the men's career record for most singles tournament wins, with 109.

Maybe one of, if not the best, strikers of the ball ever. Hits the ball very clean, taking time away from the opponent. A great competitor, a great mover. Just a smart player. He knew his capabilities and his opponents' weaknesses. He loved having a target when guys came in. He would pass you every time. -- Pete Sampras

Greatness was predicted for Agassi even before he turned pro at age 16. He proved worthy of the hype six years later, when he won his first Grand Slam title at Wimbledon in 1992. Agassi, seeded No. 12, defeated Boris Becker and John McEnroe on his way to the final, in which he outlasted Goran Ivanisevic in five sets. Agassi was a flashy pitchman who made a major splash in the endorsement world. He went on to win seven more Grand Slam singles championships, two Davis Cup titles and an Olympic gold medal.

Very aggressive. She always wanted to be at the net. She had, I think, the most technically sound volleys of anyone in that era. She was a great competitor, fearless out there. She hated to lose. She had the best backhand in the game. It was versatile, topspin or slice. -- Chris Evert

Many observers know King best for her historic victory over outspoken former Wimbledon men's champion Bobby Riggs in the famed Battle of the Sexes in 1973. Riggs had repeatedly disparaged female tennis players and boasted that, even at age 55, he could beat King. Instead, King beat Riggs in straight sets to earn a $100,000 payday that was witnessed by an estimated 50 million television viewers. Much more impressive, however, are her record 20 Wimbledon championships -- six in singles, 10 in doubles and four in mixed doubles.

The biggest thing was how athletic she was. She was a terrific serve-and-volleyer. One thing that really helped her was our coach, Harry Hopman, who would bring her down to [men's] practice. She felt that working with the guys gave her a bit of an edge. Speedwise, she was the fittest of all of us. -- Rod Laver

It's not easy to identify the career zenith of a player who won a record 24 Grand Slam singles championships and another 40 in doubles. But even in that context, the streak Court enjoyed from January 1969 to January 1971 is extraordinary. She won eight of the nine Grand Slam singles titles during that span, including six in a row and the first women's Grand Slam of the Open era.

I feel he changed the game of tennis in 1984. He was serious about nutrition and training in a way we haven't seen. Today, it's something all professionals do. He was way ahead of it. On the court, he was very, very consistent and mentally strong. He always wanted to make improvements. -- Stefan Edberg

At a time when John McEnroe and Jimmy Connors were the dominant names in men's tennis, Lendl managed to elbow his way into the conversation by achieving a No. 1 ranking in February 1983. He cemented his place among the sport's elite the next year with his first Grand Slam tournament win by rallying from a two-set deficit against McEnroe in the French Open final. The Czech held the No. 1 ranking for 270 weeks over the course of his career, third only to Roger Federer and Pete Sampras.

He had a lot of power. You had to really play well and, most importantly, steady to beat him. The style he played was a very difficult style to play against. When he was on -- which was most of the time -- you had to withstand it. When he wasn't, you had to take advantage of his weaker moments. -- Ivan Lendl

Becker is the youngest male champion in Wimbledon singles history, having stunned the tennis world at age 17 in 1985. He was also the first German to claim the men's Wimbledon title. He won three of his matches in five sets before recording a four-set championship victory over Kevin Curren.

She got a really raw deal. She would have won six to eight more Grand Slams if she hadn't been stabbed. She might have set the record. Remember, she was No. 1 when it happened and missed nearly three years. No one took the ball earlier and created more acute angles. She was tenacious -- just dictated almost every point. -- Chris Evert

Seles began a two-year domination of her sport at age 17, when she assumed the No. 1 world ranking. She won seven of nine Grand Slam events from January 1991 through January 1993. Her career took an unfortunate turn when a crazed fan stabbed her during a match in April 1993, which led to a two-year playing hiatus. She went on to win the 1996 Australian Open but never returned to the level of her previous success.

He was Mr. Consistency. Good at both singles and doubles, and that's the one thing that had him playing all the time. Maybe that's why, from my standard, he was the fittest player on the circuit. He had a great, great backhand. He was also one of the quickest players on the court, and when he'd serve and volley and get to net, he hit a lot of nice deep volleys. You could not pass him. -- Rod Laver

In 1964, Emerson missed becoming the third man to achieve the Grand Slam. He won Wimbledon, the Australian and the U.S. championships but failed to defend his French title from the previous year. Emerson is the only man who won the career Grand Slam in both singles and doubles and the only man who won five consecutive Australian singles titles. He shares the record of six Australian Open men's singles titles with Novak Djokovic.

He was most noted for the famous backhand. He hit the ball very flat and hard and heavy. A very good serve and complete all-court game. Look at all the titles he won. That tells you the kind of competitor he was. -- Roy Emerson

The year 1938 represents a landmark in tennis history. That's when Budge became the first player to achieve the Grand Slam, as he won each of the major championships in the same calendar year. If that weren't enough, he captured the Davis Cup as a member of the U.S. team and became the first player to win Wimbledon without losing a set that year. Budge also won 92 consecutive matches from early 1937 to late 1938.