It has become the must-have play for any serious postseason team: a pick-and-roll involving a wing ball handler and whichever teammate is being defended by the opposing point guard. It is a way to yank the other team's weakest defender, and often its most important offensive player, into untenable mismatches.

The Celtics knew every playoff opponent would try it against Isaiah Thomas, but not every team has Jimmy Butler -- a bruising, creative ball handler who can rain fire from midrange and bulldoze little guys in the post. Editor's Picks Zach Lowe's NBA awards picks: MVP, DPOY, ROY and more

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In the early part of the series, Chicago had Butler screen for Rajon Rondo, an arrangement that didn't inflict as much pain, because Thomas could skitter under Butler's screens and dare Rondo to chuck. But over the past two games, and especially in Game 4, the Bulls targeted Thomas by having his man -- now Isaiah Canaan, assuming Rondo doesn't make some superhuman return from a broken thumb -- screen for Butler on almost every possession.

The Celtics tried to have Butler's man dip under those screens and meet him on the other side, so that Thomas could stay on Canaan instead of switching onto Butler. That is easier theorized than done. Sometimes, they've had Thomas lunge at Butler, impeding his drive, before recovering to Canaan somewhere along the 3-point arc -- hopefully before Butler can whip the ball to Canaan for a pick-and-pop triple.

And sometimes, they've just eaten the switch. Thomas is 5-9, but he's stronger than brutes anticipate.

"He's a tough, stocky little dude," said Miami's James Johnson, who formed one of the league's best wing-point guard pick-and-roll tandems this season with Goran Dragic. "He gets low. And when you try to back him down, he pulls the chair on you. He's got a lot of antics."

No set of antics can hold Butler for long. The Celtics can help Thomas by flooding Butler's side of the floor:

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That might coax Butler into swinging the ball, and depending on the shot clock and Chicago's level of focus, he might not get it back.

But letting Butler bludgeon Thomas over and over is not ideal. It risks fatigue and foul trouble for Boston's offensive engine. The Celtics can hide Thomas on Paul Zipser, but it takes only one possession, or maybe half of one, for Butler to register that and bring Zipser (and Thomas) up for a pick-and-roll.

So toward the end of the third quarter in Game 4, Brad Stevens unveiled an alternative -- a zone-style defense that basically amounted to cloaking Thomas in a game of hide-and-seek:

After every Boston basket, Thomas ran back into one of the corners. Butler would bring the ball up and find a wing player on either side of him, usually Avery Bradley and Marcus Smart, with some Jae Crowder mixed in. One Celtic would shadow Butler. The other stood sentry until someone else set a screen for Butler. The Celtics were preemptively switching Butler-centric pick-and-rolls with like-sized defenders before the pick-and-roll even happened.

In that clip, you can see Thomas on Canaan in the left corner. Butler sees it, too, and waves Canaan up. But Thomas stays put; Smart is already there, waiting for Canaan. Thomas found the nearest Bull, and the whole Boston defense changed shape in response to Butler's next action. Butler could, of course, call Thomas' new mark up for a pick-and-roll, but Boston would repeat this Whack-A-Mole as the shot clock ticked away.

The little gimmick took Chicago out of its rhythm as Boston salted away the game. If the Bulls were going to attack Thomas, they would have to do some gymnastics to find him, and they'd find him on the wing, where the Celtics could use the sideline as an extra defender.

This isn't rocket science. Chicago will be ready for this in Game 5, assuming Stevens even uses it. There are obvious counters, including all the usual ways to beat a zone. If two Celtics sandwich Butler, one Bull can flash to the foul line, catch a quick pass, and survey a 4-on-3. Put a little extra shooting on the floor, and those 4-on-3s are death to a zone.

Mismatches generally emerge as offensive players dart around, and the Bulls might be able to find a good post-up someplace -- or just pounce on a scramble situation:

Chicago tried having Canaan rush to screen for Butler at half court, before Thomas could retreat into hiding, but Boston was ready for that:

Smart sniffs out the Canaan pick, snaps into duty, and orders Thomas the hell out of harm's way. Smart, Bradley and Crowder are like older brothers stepping in between Thomas and his bullying playground tormentors.

But Thomas ends up on Dwyane Wade, still a dangerous one-on-one threat against smaller guards. Chicago gets the Butler-Thomas matchup, anyway. It doesn't produce a good look -- Wade bonks that triple -- but the play shows the Bulls can pick this defense apart if they get into their offense fast enough.

It will be interesting to see how this cat-and-mouse game evolves in Game 5 and whether other teams with vulnerable point guards ape Stevens' strategy.

Other thoughts on a weird 2-2 series:

• Chicago has to try something else when Thomas and Al Horford run a pick-and-roll against Robin Lopez, surrounded by three shooters in the small-ball groups that have flipped the series. Fred Hoiberg has had Lopez slide along with Thomas at the point of the screen, usually around the 3-point arc, and Thomas has just sliced Lopez apart. He zips around him, splits defenders, bounces a pass to Horford rolling into a 4-on-3 -- all fatal blows to Chicago's defense.

Lopez just doesn't have the mobility to hang with Thomas out there. Boston scored 1.205 points per possession over Games 3 and 4 on shots that flowed out of a Thomas pick-and-roll, per Synergy Sports. That includes Thomas' own attempts and shots from teammates one or two passes removed. That figure would have led all high-volume pick-and-roll ball handlers in the regular season, per Synergy.

Cristiano Felicio fared better trapping Thomas in Game 3 but has faded since; Hoiberg yanked him after a botched assignment in the first half of Game 4, and he never saw the floor again. Hoiberg went without a true center down the stretch of that game, using a Nikola Mirotic-Bobby Portis frontcourt. There was even a surprise appearance from King Joffrey Lauvergne.

You could see the reasoning, at least. The Mirotic-Portis combo offered more speed, switchability, and shooting -- the latter being key around Butler and Wade.

But Lopez's rebounding, screening and midrange shooting have been elemental to whatever success Chicago has had. Boston even started sending an extra defender into Lopez's line of sight on pick-and-pops, opening up new passes:

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Going small generally works because it involves putting your five best, most skilled players on the floor. That is not the case for Chicago. The Bulls are probably not going to win this series on Boston's terms. They might not win it on their terms, either, but there is an in-between point somewhere.

I don't know what the answer is. Maybe they should have Lopez hang back, and rely on Canaan -- and other Chicago defenders -- to stick on Thomas' hip around screens, so that Thomas can't launch off-the-dribble 3s. That's a gamble; Thomas hit 37 percent of his pull-up 3s this season (and 34 percent last season), and if Canaan falls behind too often, Thomas will drain daggers. Maybe they should just have Lopez sell out and trap, forcing Thomas to retreat toward midcourt and give up the ball. Now that Boston has gone small, there really isn't another hiding spot for Lopez on defense.

Sometimes the best adjustment is to do nothing and just execute better. I don't think that's the case here.

• Boston should keep running variations of the Thomas-Horford dance until Chicago stops it. When the Celtics get too cute, bad stuff happens. They opened the second half of Game 4 with a pindown for Gerald Green, who proceeded to turn the ball over. In the fourth quarter, Horford ambled up to screen for Thomas, but before he got there, Thomas tried to slip him an entry pass -- presumably to then take a handoff from Horford -- through a crowd. Chicago stole it and ran out on the break.

Variety is important, but not when the other team has shown no response to your bread-and-butter. Keep it simple.

• I liked Chicago trying Canaan over Jerian Grant and Michael Carter-Williams. The Bulls don't need a non-shooting ball-pounder next to Butler and Wade. They need Patrick Beverley, but they don't have Patrick Beverley. Canaan has been a disaster in Chicago, but his 26 percent mark from deep this season is an outlier. He hit 36 percent last season, and 40 percent of his catch-and-shoot triples, the kind he'll get spotting up around Butler. (He hit only 33 percent of those attempts the season before but drilled 43 percent of his pull-up 3s. Canaan has had a bizarre trek through the NBA.)

Grant hit 37 percent from deep this season and 40 percent after the All-Star break. He has wobbled against Boston's pressure defense, but he deserves some time. Carter-Williams probably doesn't. You can almost hear the backboard shrieking in terror when Carter-Williams winds up for a floater. Thomas is ignoring both Grant and Carter-Williams to clog the lane:

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Chicago might at least consider Denzel Valentine. He's a defensive liability, but he can hang against some Boston lineups.

Chicago should play a little longer without a traditional point, though that might not be the silver bullet. Butler, Wade and Zipser -- the most likely perimeter trio in such lineups -- logged only 69 minutes together in the regular season, and opponents outscored Chicago by 10 points in that time, per NBA.com. Even in the playoffs, Chicago has mostly used those three alongside one of their point guards in small-ball lineups, a setup Hoiberg might want to look at again.

• Boston's guards have been doing their best to gang rebound since Game 3. It has only stemmed the tide a bit, but that is enough.

• Butler is Chicago's best option on Thomas, but he's not quick enough to stay in front of him one-on-one. No one is. With the floor spread, Boston might want to just clear out and let Thomas isolate against Butler instead of sending someone to screen for him.

• An important subplot: how Boston fares in the precarious minutes with both Thomas and Horford on the bench -- 27 minutes through four games. Boston's four-man bench mob -- Smart, Jonas Jerebko, Kelly Olynyk, and Terry Rozier -- is plus-6 through 14 minutes, and it extended Boston's lead in the second quarter of Game 4. The group has found weird ways to manufacture buckets: designed post plays for Smart, Olynyk's herky-jerky slow-motion drives and other stuff.

Boston rounds out that group with one starter, usually Bradley or Crowder. Chicago needs to win those minutes. The Bulls need to win any minutes Thomas rests. Boston fell apart in the third quarter of Game 4 when Thomas sat with foul trouble, even though Boston's four other starters stayed on the floor. Boston's offense has fallen into a sinkhole without Thomas all season.

• A subplot within the subplot: the battle between Wade and Olynyk on the pick-and-roll during the second quarter, when Butler rests. Wade goes at Olynyk every time, with the help of some nasty screens from Felicio, a grinning human cinderblock.

• Boston has thrown some occasional traps at Butler on the pick-and-roll. Something to monitor.

It feels like Boston has solved this series, but just when you think you can predict the future, wacky stuff happens. On to Game 5 ...