New Bucks head coach Mike Budenholzer has done everything right in his first few months on the job. Milwaukee has made a dramatic turnaround from last season, going from winning 44 games and losing in the first round to having the best net rating (plus-8.5) and the second-best record (21-9) in the league. The only big personnel change has been the addition of Brook Lopez, whom the team signed to a one-year, $3.3 million contract in the offseason. His impact in Milwaukee goes far beyond his relatively average stats: 11.8 points on 42.7 percent shooting, 4.1 rebounds, and 1.9 blocks in 27.7 minutes per game. He filled the two biggest holes on the Bucks roster. They didn’t put enough 3-point shooting around Giannis Antetokounmpo, and they ran an outdated defensive scheme that conceded too many open 3s. Lopez gave them a stretch 5 to open up the floor on offense and a presence at the rim to tighten up their defense.

Lopez has allowed everyone else to thrive in their new roles under Budenholzer. The question for the Bucks is whether he can be as effective in the playoffs, and what their Plan B is if he can’t.

Lopez is a real-time example of the evolution of the game. He came into the NBA as a post scorer and has slowly turned himself into a jumbo-sized shooting guard. At 7-feet and 270 pounds with a 7-foot-6 wingspan, he has always had great touch and footwork for a player his size. He’s just using those skills to launch 3s instead of hook shots. Lopez takes 70 percent of his field goal attempts from behind the 3-point arc, a higher percentage than all but three other starters in the league this season, none of whom are taller than 6-foot-6.

No other center stretches the defense like Lopez, who is shooting 36.6 percent from 3 on 6.8 attempts per game. The gap between him and the no. 2 center in 3-point attempts (Karl-Anthony Towns at 4.6) is as wide as the one between Towns and no. 13. A big man with his shooting range changes the way teams play defense. Defenders have to stay attached to Lopez to even bother his shot. His release point is so high that he can shoot over most close-outs, and he has the ultimate green light in Budenholzer’s offense. Lopez will launch from anywhere on the court at any time on the shot clock. It doesn’t matter how slow he’s moving; there’s nothing a defense can do when he’s making step-back 3s:

The Bucks have been a different team with him on the floor. They go from having what would be the highest offensive rating in NBA history with him (115.6 in 832 minutes) to a bottom-five offense in the league without him (103.9 in 618 minutes). It’s a perfect match of player and situation. Milwaukee doesn’t have many players who can handle the volume 3-point-shooting role necessary for Budenholzer’s offense to click, and it has four scorers (Giannis, Khris Middleton, Eric Bledsoe, and Malcolm Brogdon) who can take advantage of the space that Lopez creates.

The downside of playing a shooter like Lopez typically comes on defense, but he has been one of the cornerstones of the Bucks’ turnaround on that end of the floor too. Budenholzer scrapped the team’s high-risk, high-reward defensive scheme from last season, which blitzed pick-and-rolls with multiple defenders but left gaps open behind the play, in favor of a more conservative one built around Lopez’s ability to seal off the paint. The change has worked. They have skyrocketed from the no. 18–rated defense in the NBA all the way up to no. 5.

The new system fits their roster. The Bucks perimeter players are using their length and athleticism to fight over screens and funnel penetration toward Lopez. Their defense protects the paint at all costs, allowing the fewest number of shots within 5 feet of the rim in the league (26.4), as well as the lowest field goal percentage (54.9) on those shots. Lopez is (literally) in the middle of it, as his combination of bulk and veteran savvy allows him to contest shots without fouling. He is one of seven players, along with Anthony Davis, Rudy Gobert, Clint Capela, Al Horford, Myles Turner, and Maxi Kleber, with both a block rate higher than 5 percent and an average of fewer than 3.5 fouls per 36 minutes of playing time.

Unfortunately for Milwaukee, Lopez isn’t nearly as athletic as the other six players on that list. Budenholzer has put him in a scheme that covers up his weaknesses, but it does have an Achilles’ heel that has already been exploited in the Bucks’ games against the other top teams in the Eastern Conference. Dropping Lopez so far back in the paint on the pick-and-roll means there’s no one to contest the shot of a big man who pops to the 3-point line instead of rolling to the rim. The great irony of how the Bucks have been using him is that it makes them vulnerable to guys who play exactly like him. Horford (Boston) and Serge Ibaka (Toronto) have taken a career-high number of 3s in their last games against the Bucks; Turner (Indiana) had a season high in his. These shots might as well be target practice:

There are no easy adjustments for Budenholzer to make. Sending an extra defender to help out on a pick-and-pop big man would just leave an open 3-point shooter somewhere else on the court, and Lopez isn’t fast enough to make a rotation outside of the paint. His lack of speed also means he wouldn’t be effective in any other pick-and-roll coverage. He can’t rotate back to the paint quickly enough if he has to pick up the ball handler farther up the court, and he can’t keep those players in front of him if they switch the screen, either.

Milwaukee has been happy to make the trade-off in the regular season. There aren’t many teams with centers who can hold up against it on defense and go shot-for-shot with Lopez from the 3-point line. That equation could change in the playoffs, when the Bucks will face elite teams who can change their game plan to mercilessly exploit a specific weakness over a seven-game series. There are certain types of players who are more effective in the regular season than the playoffs. The Warriors call them 82-game players as opposed to 16-game players. Lopez, who has never been out of the first round in 10 seasons in the NBA, might be one of them.

The problem for the Bucks is that Lopez is too essential offensively to minimize. They don’t have enough 3-point shooting without him. They are no. 2 in the NBA in 3-point attempts per game (39.9), but only no. 14 in 3-point percentage (.350). Budenholzer staggers his lineups as much as any coach in the league, and he almost always keeps at least one starter on the floor. The one constant amid all his shuffling has been the positive impact that Lopez makes. Their other four starters all have significantly better offensive ratings when they are playing with Lopez, regardless of who else is in the game:

How Lopez’s Presence Impacts His Teammates Bucks Starters Offensive Rating With Lopez Offensive Rating Without Him Bucks Starters Offensive Rating With Lopez Offensive Rating Without Him Antetokounmpo 114.0 (582 minutes) 102.1 (333 minutes) Middleton 116.0 (604 minutes) 102.3 (232 minutes) Bledsoe 114.8 (660 minutes) 103.3 (211 minutes) Brogdon 112.1 (470 minutes) 99.6 (339 minutes)

Not even Giannis, who is putting up MVP-caliber numbers while scoring at the rim at rates we haven’t seen since prime Shaq, has been able to match the impact that Lopez has on offense. Milwaukee has an offensive rating of 113.0 in 233 minutes with Lopez and without Giannis and an offensive rating of 104.3 in 350 minutes (which would be tied with the Magic for no. 27 in the NBA) with Giannis and without Lopez. The team still has players like Middleton and Bledsoe who can run the offense and attack the rim when Giannis sits, but it doesn’t have enough shooters to space the floor when Lopez does.

The Bucks have had to restructure their lineup around Giannis in the minutes when Lopez sits. Those lineups have succeeded in spite of their woeful offense by clamping down on defense, with a minuscule rating of 93.8 that would lead the league by 7.9 points. Giannis, at 6-foot-11 and 242 pounds with a 7-foot-3 wingspan, is an absurd athlete who can cover up the floor and defend all five positions with ease. Put four other high-level athletes around him, and they can lock up teams. Milwaukee essentially has two identities it can toggle between: a dominant offensive team that has one glaring defensive weakness with Lopez and a dominant defensive team looking to score just enough to survive with Giannis.

Giannis is the one constant in both lineups. The Bucks need him to cover for Lopez on defense and carry the offense when Lopez is out. Budenholzer will have to keep his starting center out of the pick-and-roll as much as possible in the playoffs, which means moving him off the center and hiding him on the weakest offensive player in the opposing team. The problem is that Giannis is Milwaukee’s only other starter who can physically match up with centers. He’ll have to do double duty in the playoffs, and the team might not be able to take him off the floor at all.

Everything in Milwaukee comes back to Giannis. He can play all five positions on offense and guard all five on defense. His versatility allows him to fill any hole the Bucks have over the course of the game. The Bucks have made a leap this season, but there are more levels to go. The East is as good as it has been in over a decade. Milwaukee may need to beat two great teams just to get to the NBA Finals. The only way that will happen is if Giannis follows the LeBron model. LeBron played all 48 minutes when he beat the Celtics in a Game 7 last season. Giannis played only 42 when he lost a Game 7 to the Celtics. The next step for Giannis isn’t developing a jumper. It’s accepting the responsibility of never coming out of a close-out playoff game. Giannis is Plan A in Milwaukee. There is no Plan B.