The Celtics had the Bucks on the ropes after securing an overtime win in Game 1 and delivering a beat down in Game 2 of this first round Eastern Conference series. Brad Stevens had Milwaukee figured out. Terry Rozier had zero turnovers in over 70 minutes of action against Drew Bledsoe. It was adapt-or-die for Milwaukee as they headed home for Games 3 and 4.

Spoiler alert: they adapted. Joe Prunty implemented a defense for his team where they would start to switch on Boston’s ball screens. The actions the Celtics run involve a lot of off ball movement with screeners and misdirection to confuse any defense that isn’t connected.

Milwaukee rarely switched on defense throughout the year even though they had the positional versatility to do so. When faced with a potential 3-0 series hole, Prunty’s defense has made the series interesting again with a physical defense with incredible length and activity.

The change has certainly affected the Celtics, who averaged 97 points in the last two games after scoring 116.5 points per game in Boston. Their field goal percentage is down from 47.4 percent to 40.7, while the three point shooting has dipped from 42.1 percent to 33.9. The Celtics’ youth struggled to adapt to the physical nature of postseason basketball, but the main issue with their offense the last two games was summed up by their opponent on Sunday.

Giannis: “When we switch, they play iso-game. And that’s not what Boston wants to do.” — Jay King (@ByJayKing) April 22, 2018

The Celtics had the seventh highest isolation frequency in the league this season, ranking in the 83rd percentile by scoring 0.93 points per possession. The “ISO-game” isn’t this Celtics team’s strength without Kyrie Irving on the floor, and they’ve played right into the Bucks’ hands this past weekend.

In four playoff games, the Celtics once again have the seventh highest isolation frequency in the NBA, but rank in the 46th percentile by scoring 0.87 ppp. Jayson Tatum has scored 0.57 ppp (10th percentile) on 14 isolation possessions, while Terry Rozier has posted 0.88 ppp on eight of those possessions.

When a defense successfully switches everything they take away the offense’s ability to screen effectively. There’s no opening on the pick and roll, and it’s difficult to free up shooters when defenders are shifting responsibility so fluidly. The counter? The offense exploits mismatches created by smaller players getting switched on to bigs and longer wings.

Thon Maker came off the bench in Game 3 and provided an immediate boost, blocking five shots in each of the two games in Milwaukee. He demonstrated the foot speed and timing to take away the advantage of a wing driving past him for an easy hoop.

On both plays you can see Tatum get Maker on the switch, size him up and proceed to have his shot blocked on the layup attempt. Jaylen Brown and Terry Rozier found success with step-back threes against Maker in a switch, but other than making a tough shot like that, the second-year Milwaukee big is not the right mismatch to go after.

As you can also notice when watching the clips above, there’s little movement from the rest of the Celtics on the floor. Spreading the floor for a drive is a fine strategy, but standing around allows the Bucks to squeeze the paint and turn missed layups into fast break opportunities. Milwaukee averaged 13.5 blocks in the last two games, leaving the Celtics to rethink their plan of attack around the rim.

Allowing the Bucks to stay still on defense also makes kick out passes harder to make. Milwaukee already has supreme length. Not forcing them to move just feeds into their defensive advantage.

An adjustment the Celtics could make going into Game 5 could be to get Maker to switch on a perimeter player, but then swing the ball to the opposite side and attack from there with more movement and back-door cutters.

If Maker collapses to chase another block, the driver needs to be ready to make that kick out pass. Even if Maker is guarding the ball handler, the Celtics should be prepared to use up-fakes and dump off passes to counter an over-committed defender.

Another way to attack the switch is exemplified in the clip above. The Celtics have Al Horford and Aron Baynes around the three point line stretching out the Milwaukee bigs. Brown screens for Rozier, causing the shorter Eric Bledsoe to switch instead of Khris Middleton. Brown then gets good position on Bledsoe before Baynes delivers a lob for a layup.

This isn’t a play the Celtics can run every time down the floor, but it’s an example of them being deliberate in attacking a specific matchup. Rather than sizing up a versatile big off the dribble for a drive into traffic, Boston can look to force Milwaukee into a scramble.

In a play that features a handoff-pick and roll with Tatum and Horford, the important action is happening on the other side of the floor. Because of Milwaukee’s switch-happy new scheme, Matthew Dellavedova gets confused when Rozier runs toward the baseline while Brown pops to the wing for an open three.

It’s a simple motion that Boston ran to get Brown a look on the wing or to the basket, but the motion away from the ball handler caused enough confusion to break down the defense.

On this marathon of a play, Maker switches on and Horford immediately does a drive and kick to Tatum. Tony Snell is late to close out because Giannis Antetokounmpo was late to get to Semi Ojeleye. Horford’s drive put enough pressure on the defense to here Tatum drove into three defenders. He then found Horford on the kick out for an open three.

Even though Horford missed, the Celtics generated a good shot and highlighted another advantage to keeping the Bucks moving. Boston has dominated the offensive glass in this series, posting a 28.6% offensive rebound percentage. With Milwaukee’s bigs switching on to perimeter players, the Celtics have a better chance at securing misses and kicking it back out to open shooters like Tatum in this scenario.

The Bucks had to make an adjustment if they hoped to keep their season alive. With Maker and a bunch of switching, they gave the Celtics a lot of trouble with their length and aggressiveness.

In a series with Irving and Gordon Hayward, Milwaukee probably doesn’t get away with this type of defense for two whole games. However, there are a lot of young players on this Celtics team getting their first taste of serious postseason playing time who will have to respond if Boston hopes to advance. The chess match continues.