The Philadelphia Eagles have exceeded expectations so far in coach Chip Kelly's first season. The Detroit Lions have arguably fallen a little short of expectations in coach Jim Schwartz's fifth season.

When the two 7-5 teams meet in Philadelphia, it won't matter how they got there. The Eagles and Lions are both in position to win their division titles, and a win Sunday will be a major step toward achieving that goal.

The game will feature two potent but very different offenses. Nick Foles may not be the bona fide franchise quarterback that Matthew Stafford is, but he is the hottest quarterback in the league over the past five weeks. The Eagles' defense may lack stars like Ndamukong Suh, but it is playing better every week as a group. Stafford, Calvin Johnson and Reggie Bush will provide its toughest test since the Denver disaster back in September.

ESPN.com reporters Michael Rothstein, who covers the Lions, and Phil Sheridan, who covers the Eagles, took a look at some key issues in a game with major playoff implications.

Sheridan: The NFC North race has been deeply affected by quarterback injuries, with Chicago's Jay Cutler and Green Bay's Aaron Rodgers out of the picture lately. Despite a healthy and productive Stafford, the Lions haven't been able to separate from the rest. What are some key reasons for that?

Rothstein: It starts with turnovers and inconsistency. The Lions' defensive line, the same group that dominated on Thanksgiving, largely disappeared in some earlier games. Turnovers are a major issue, too. The Lions have three or more turnovers in four of their past five games. Against Tampa Bay and Pittsburgh, that was a key factor in those losses. Detroit is a very talented team that continues to feel like a group still finding out exactly how it wants to play. But it does start with those turnovers. A couple of the Lions' players even told me after Thursday's game -- by far the Lions' best performance this season -- that turnovers were still a major issue. And Detroit committed four of them and still scored 40 points. If they do that Sunday, the Lions will be leaving with a loss.

Speaking of turnovers, Foles appears allergic to mistakes, especially turnovers, this season. Is it all fitting in with Chip Kelly's system? Maturation? Magic? Something different? What has turned him into this quarterback this season?

Sheridan: There is almost certainly an element of magic involved. By that I mean that Foles has had a bit of luck on his side. He threw two would-be interceptions to Patrick Peterson Sunday, for instance. DeSean Jackson batted one away and a penalty negated the other. But there is no doubt that Foles has played extremely well and with remarkable poise and confidence. He has fully embraced and absorbed Kelly's offense, which includes sound pass protection and a great running game -- two of every quarterback's best friends. Foles has been accurate and unafraid to trust his receivers to make plays on the ball. If you make good decisions and sharp throws in a well-designed offense, it turns out pretty much like what we've seen from Foles the past two months.

The Eagles felt pretty good about running their offense effectively against good Tampa Bay and Arizona defenses. The Lions seem like a new challenge with that front of theirs. Was the Thanksgiving game a sign the Lions have gotten it going on defense or are they just as likely to disappear in the face of Kelly's uptempo, unorthodox offense?

Rothstein: It's tough to say because the Lions haven't really seen this type of offense before, although I'm guessing the three younger guys on the line -- tackle Nick Fairley and ends Ziggy Ansah and Devin Taylor -- are somewhat familiar from their recent college days. Getting pressure with the front four -- and, at least last week, well-timed blitzes from linebackers and safeties -- is still going to be the key for any Detroit defensive success. And doing it for one week doesn't make it a guarantee that it'll continue. Even though he doesn't have huge stats, Suh has been a consistent force up front and if he and Fairley can get going early, it opens things up for Ansah on the outside.

The pressure key, though, is more important for Detroit's cornerbacks. The Lions have been very inconsistent there this season, but they were able to take the first read away from Green Bay's Matt Flynn a lot. By doing that, it gave the defensive line an extra second to get to Flynn so it all worked together. But it has been a matter of consistency, which the Lions have not had there this season.

Since we were talking about the Detroit defensive line, the Lions have been extremely good against the run. They haven't allowed a rushing touchdown in two months and have gone six straight games holding teams under 70 yards rushing total. Some of this is the proliferation of passing in the NFL, but considering LeSean McCoy's numbers this season, how much do the Eagles try running before sticking with Foles and his arm?

Sheridan: One of the most striking differences between Kelly and Andy Reid, a guy I covered for 14 years and respect a lot, is that Kelly is very committed to the run. He sticks with it almost no matter what, with the belief that it will eventually wear a defense down. Reid would abandon the run game after two or three unsuccessful plays. Early in the season, McCoy was on pace to break the NFL record for rushing attempts in a season. He is now on pace for 100 fewer carries than that, about 310. That's because Foles' success in the passing game has allowed Kelly to be more balanced. A few teams -- the Giants and Cowboys, especially -- were able to shut the Eagles' running game down. Arizona did a good job of it in the second half. But Kelly hasn't completely abandoned it in any of those games. If that changes Sunday, it will mean he really thinks the Lions' defense is invulnerable to it.

The Eagles were moderately successful keeping Larry Fitzgerald from going off last week. Johnson is another matter. Has anyone been really effective in stopping Megatron and, if so, how did they go about it? Does it take an elite corner or an elite scheme? A drone strike?

Rothstein: The team that has been most successful in limiting Johnson this season has been ... the Detroit Lions. There have been times during games this season when the Lions have seemed to go away from the best receiver in football, most notably in the second half against Pittsburgh, when he had no catches. Darrelle Revis has been pretty good on Johnson as well, but for the most part, it takes a really good scheme to keep the ball out of his hands. Unless you have a corner like Revis, usually some sort of bracketing of Johnson can be effective. But the Lions are OK with that happening because it opens up the field for Bush and Nate Burleson. That was a big reason the Lions got Bush -- just for that.

This kind of leads into my last question. Philadelphia's pass defense has been both poor and porous this season. Do they have any sort of manpower to match up with Johnson -- and to a lesser extent Burleson, Brandon Pettigrew, Kris Durham and Bush -- or could this be another game like he had against the Cowboys or Bengals?

Sheridan: Before getting to the answer (spoiler alert: It's no, the Eagles can't match up with Johnson), let me clarify a bit. It's true that the numbers show the Eagles to be terrible as far as yards allowed. They really have given up vast chunks of yardage. But they are keeping teams out of the end zone, and that is giving the offense breathing room to function.

While insisting the Eagles' defense is better than its stats, I have to say this matchup could be the one that breaks some of those trends. Stafford is better than Carson Palmer and Johnson is better than anyone, so this may be the week the yards translate into more points. The Eagles' strength right now is their front seven, and if they can get pressure on Stafford and force him into some of the mistakes he is prone to making, that will go a long way toward covering up the mismatches on the back end.