It’s not as if this recent stretch of “blah” basketball is unprecedented for Miami. The Heat started off a mess on defense last season, hemorrhaging 3-pointers, and they ranked just 23rd in points allowed per possession at the one-quarter mark of what ended as a championship campaign. They even endured a midseason malaise at almost this exact time of year — a stretch from December 28 through January 14 in which Miami went 4-6, outscored those 10 opponents by just 14 total points (awful by their standards), and generally looked mortal during a road-heavy chunk of the schedule.

Flash-forward almost a year, and Miami is an uninspiring 6-4 in its last 10 games, with a disappointing (by their standards) plus-27 scoring margin in that stretch and a defense about to slide out of the top 10. The issues on defense date back further. The Heat over their last 20 games have allowed 105.2 points per 100 possessions, a mark that would rank about 22nd overall — tied with Milwaukee, Brooklyn, Dallas, and Detroit. Turns out Miami’s defense didn’t really right itself, in a prolonged sense, after the now-expected shaky start.

Again: There are mitigating factors. Four key players have been in and out of the lineup over a road-heavy segment of games: Mario Chalmers, Shane Battier, Chris Andersen, and, of course, Dwyane Wade. And the Heat’s defense is leaking in the same ways it has leaked before — allowing a lot of open 3-pointers and offensive rebounds. The Heat over the last two seasons have overcome what should have been fatal flaws, in part because their roster and system are built to produce other goodies at unusual rates — opponent turnovers, their own wide-open 3-pointers, etc. And Miami has cleaned up those weaknesses in the playoffs. Before their 2012 title run, only one team since the 1999 lockout — the 2006 Heat — had even made the Finals after allowing both an above-average number of 3-point attempts and an above-average field goal percentage on those 3-point shots. Only two such teams had even made the conference finals in that span. Miami in that season met both “bad” criteria quite easily, but in the playoffs, their opponents hit just 30 percent from long range.

They repeated the trick to some degree last season, allowing two fewer opponent 3-point attempts per game and sealing off corner 3s almost completely, per NBA.com.

This is, in other words, a “flip the switch” team. We’ve seen Miami dial up its blitzing defense in must-win moments, reaching a frenzy that can overwhelm even a team as polished as San Antonio. History says we should shrug off any regular-season struggles as a blip on the radar for a team waiting on May.

And yet: I’m worried this is something different for Miami — that this prolonged stretch of bad defense is evidence of deeper issues that will persist into meaningful playoff basketball. Miami did not have a sustained period of bad defense like this last season after its poor start. The Heat tightened things up after a rough first 20 games, and though there were little two-game and three-game slumps scattered about, they were basically a very good defensive team continuously over the final 50 or so games. They did win 27 straight, after all.

The injuries have also reached a worrisome point. Wade has already missed 12 games this season, even though Miami swore up and down during the preseason it was not interested in using a Spurs-style “maintenance” program. He played four games in six nights earlier this month, an encouraging sign, but followed that by sitting out three consecutive games heading into Thursday night’s non-showdown with the Lakers. The Heat are mum about Wade’s knee issues, but the unpredictable nature of his availability is troubling. Wade even took to Twitter this week to assure fans that he’s trying everything to get, and stay, healthy.

Udonis Haslem is a fringe rotation player now, and has lost more than a step after suffering prolonged foot issues over the last couple of seasons. That removes a veteran leader who grew up playing the Heat’s unique style of defense, someone the Heat have been able to count on for productive spot minutes upon demand at key playoff moments.

Battier has not been the same this season. Battier, even as just a role player, is crucial to Miami’s identity. He missed several recent games with a quadriceps injury, and two-plus seasons of banging with the David Wests and Carlos Boozers of the world have clearly taken their toll. Battier is playing about 4.5 fewer minutes per game this season, attempting fewer 3s, and spending entire games as a bit player nailed to the bench.

Michael Beasley and Rashard Lewis are around to play Battier’s role as the nominal power forward with 3-point range in smallish lineups, but it’s unclear whether either is up to the task. Lewis is a nice story. He’s played in 40 games, already nearly matching his minutes total from last season, and he has shot well, played hard, and tried his best. But he’s old, and he has logged less than 10 minutes in three of his last five appearances.

Beasley has shot well on a minimum salary, but he has basically fallen out of Erik Spoelstra’s rotation over the last month. He still takes too many long 2-pointers for the team’s taste, and he has never been anything like the kind of strong, active, smart defender Miami’s system requires. Mike Miller is not here anymore to provide instant shooting, rebounding, and passing off the bench in case of emergency.

The Heat over the last two seasons reinvented themselves as a small-ball scoring machine built upon killer shooting, intricate motion offense, and a furious trapping defense. Battier spotted up for 3s and guarded power forwards so LeBron wouldn’t have to, Bosh stretched his range, the read-and-react playbook expanded, and Miami became unguardable.

Now they’re scrambling to maintain that rotation. LeBron has played more minutes without Wade this season than with him, per NBA.com. Spoelstra has compensated for uncertainty on the perimeter by playing Norris Cole and Mario Chalmers together more, an ultra-small look that will be untenable against some lineups (the revamped Nets come to mind). Bosh and Andersen have already played nearly twice as many minutes together this season as they did in 2012-13, evidence of Battier’s minutes reduction and Spoelstra’s searching for the right matchups against bigger teams.

Even more interesting: The Heat have moved away from the blitzing defensive style that made them special — the manic trapping that ended Linsanity, flustered Tony Parker, and goaded Indiana into an endless reel of ugly turnovers in Game 7 of last season’s conference finals. I noted it first during Miami’s win last month over Indiana, but it has continued since: There are stretches of games in which Miami’s defense looks very much like the basic conservative defense most of the league plays.

When the Heat are at peak mania, their big men trap pick-and-roll ball handlers with an unmatched fury — sometimes chasing them all the way toward midcourt, driving them backward, arms spread wide, awaiting deflections and steals. It’s a risk-reward thing. The risk comes in placing two defenders on one opposing point guard, so that if the point guard can unload the ball cleanly, Miami will be facing a temporary 4-on-3. Dealing with that kind of crisis requires pitch-perfect rotations, crazy athleticism, and insane effort levels. Miami has met that test more often than not.

But over the last six weeks, Miami has often ditched the trapping, electing to have the big man guarding the screener drop back toward the paint, hoping to corral the ball handler without committing to such a hard trap. It’s a speedier version of how Indiana, Chicago, and many other very good defenses handle the pick-and-roll.

Here’s Bosh dropping back against a Gerald Henderson–Al Jefferson pick-and-roll during last weekend’s overtime win against Charlotte:

And here’s Battier doing the same against a Shelvin Mack–Pero Antic pick-and-roll during Monday’s wild loss in Atlanta:

Here are a couple of examples from Miami’s completely uninspiring home win Tuesday against Boston:

There are still two defenders tracking one ball handler, but the big man in this kind of defense sort of tracks two players at once instead of committing whole hog to the point guard. He’s also closer to the paint, which in turn allows the other three Heat defenders to stay a bit closer to their own guys instead of rotating around the floor like madmen.

The Heat don’t do this all the time — not even close. There are entire possessions on which they’ll trap every single pick-and-roll an opponent throws at them, and other possessions where Miami will mix up traps and drops. But even mixing it up marks a massive transformation for a team that talks constantly, and with great self-importance, about its “identity” and “building habits” and all of that.

I suspect two things are behind the change:

1. Teams Have Caught Up to Miami

More teams know how to attack Miami’s style now, especially teams with mobile big men capable of setting a high screen, catching the ball 20 feet from the rim, and doing damage from there as a triple threat — a guy who can shoot, dribble, and pass.

Teams have gotten smarter about having those guys set the pick, lure Miami into a trap, and then cut hard and early toward the rim — making themselves available for a quick escape pass and putting Miami into that 4-on-3 situation. A lot of teams call this a “shallow roll” — a roll designed for the big man to catch far from the hoop, instead of right at the rim for Tyson Chandler– or Andre Drummond–style pick-and-roll dunks.

Here’s Paul Millsap pulling off the trick for this week’s wild Atlanta win over Miami by running up to set a pick for Shelvin Mack, noting the Miami trap, and then cutting back toward the paint without really even setting the screen:

Plays like this are part of the reason Heat opponents have hit a stunning 45.6 percent on corner 3s this season, by far the highest such opponent percentage, on nearly seven attempts per game — the third-highest mark in the league. David Lee murdered the Heat on plays just like this during Golden State’s win in Miami on January 2. David West is good at this kind of stuff, but he’s not quite as well rounded or quick-thinking in open space as the very best outside-in big men. The Heat close windows faster than anybody, and if West were just a hair better at picking out open shooters in the tiny slice of time available, the Pacers might have made the Finals last season.

Dialing back the traps is Miami’s way of making teams play them honest — of removing the built-in 4-on-3 that leads to so many open 3-pointers, and forcing teams to work a little harder. But it also runs counter to everything for which Miami stands, and against a smart and well-prepared playoff team it might result in Miami forcing fewer turnovers. The Heat still lead the league in opponent turnovers per possession, and they top that category even over these last 20 ho-hum games. But the league’s overall turnover rate typically drops in the postseason, and it stands to reason that Miami might sacrifice some steals in the name of stylistic conservatism. There are trade-offs to everything in basketball.

2. Father Time Is Creeping In

The adjustment might also be Miami’s recognition that it is just too exhausting for an older team to play so frantically all the time — both physically and mentally. Miami’s postseason runs have been littered with bizarre defensive slumps. They allowed the 2012 Celtics, an atrocious scoring team, to absolutely light Miami up over the first five games of the conference finals. Last season’s Pacers, a below-average offensive team, did the same over the first six games of last season’s conference finals, and I’m pretty sure Danny Green just hit another wide-open 3-pointer against Miami.

Miami’s opponents deserve credit for some of that surprising scoring. Teams focus all their scouting resources on one opponent during a playoff series, and both the Pacers and Spurs introduced some very smart anti-Miami tweaks last season. But a lot of those enemy open looks came off of confounding Miami breakdowns — horrific transition defense, botched switches, and lots of instances in which Miami players simply spaced out and lost track of their assignments.

They were the mistakes of a fatigued, addled team close to the finish line. Yes, the Heat have proved in elimination games that they can summon the requisite effort. But they’ve been on the precipice several times, and no team, no matter how confident in its switch-flipping, wants to take things all the way to the last minute. It’s a dangerous game.

The switch in style could preserve some energy, both now and in the postseason. Maybe the Heat will revert to the all-blitz strategy when the playoffs become competitive. But the Heat might also see value in using multiple strategies — in engineering some unpredictability.

It’s not all doom and gloom. Miami should coast into the conference finals, and when the inevitable Pacers-Heat matchup happens, Miami in that series will face a turnover-prone team with ball-handling issues. All smart teams adjust, over the short- and long-term.

But the Heat’s level of play is worth monitoring now. There’s something a bit uneasy about them. A team that found a championship identity and spoke reverently of its importance is scrambling a bit to find a slightly altered one for a new season of challenges.