Six things to watch in the Celtics-Heat Eastern Conference finals

The Celtics won two of their three matchups against Miami this season.Matthew J Lee/Globe staff

Here are six matchups, trends, and injuries to watch when the Celtics face the Heat in the Eastern Conference finals.

1. In a zone

When the teams met in the 2020 conference finals in the Orlando bubble, the Heat stifled the Celtics with their zone defense. And that tactic remains a key part of coach Erik Spoelstra’s arsenal.

The Celtics struggled against zones at the start of this season, but their roster has been remade since then. Mediocre-to-poor shooters such as Romeo Langford, Dennis Schröder, Josh Richardson, and Enes Freedom are gone, and capable options such as Payton Pritchard and Grant Williams have stepped into larger roles.

“We know that’s one of their wrinkles defensively, a team that uses it quite a bit compared to other teams,” said Celtics coach Ime Udoka. “I think more so than us struggling against a zone; we struggled a little bit earlier in the year but I thought we found our groove later and did really well against it, where teams tried it, we scored pretty well against it and they got out of it. So we have multiple sets that we love to run against zone.”

Udoka said that when a zone leads to open shots, defenses tend to view it as a success if those shots miss. So the Celtics just have to convert.

2. Slowing Jimmy

Heat star Jimmy Butler has been a force in these playoffs, averaging 28.7 points, 7.6 rebounds, 5.4 assists, and an NBA-best 2.1 steals per game. Miami has outscored opponents by 16.1 points per 100 possessions with Butler on the court, and has been outscored by 1.6 when he sits.

As always, defending him will be a group effort, and the Celtics’ switch-heavy scheme will dictate matchups.

Miami's Jimmy Butler will test Boston's tenacious defense.Matthew J Lee/Globe staff

Although Marcus Smart was the NBA’s Defensive Player of the Year, the 6-foot-7-inch Butler could have success shooting over him, so the Celtics likely will open up with a bit more length on the veteran forward. Also, Smart suffered a foot sprain in Game 7 against Milwaukee and will be listed as questionable for Game 1 Tuesday.

Perhaps Jaylen Brown or Jayson Tatum will get the first shot, but the Celtics are aware of tiring out their stars on defense.

Butler also is one of Miami’s top defenders, so look for the Celtics to go out of their way to make the 32-year-old work at that end of the floor in an attempt to wear him down.

3. Tatum time

Tatum struggled a bit during three games against the Heat this year, averaging 17.7 points — nearly 10 below his season average — and shooting 5 for 17 from the 3-point line. Against the Bucks, there were obvious mismatches for Tatum to hunt, but those opportunities will be less obvious against a gritty Miami defense that ranked fourth in the NBA this season, by far the best of any Boston playoff opponent so far.

Duncan Robinson has been used sparingly by Miami in the playoffs, but if Spoelstra decides he needs Robinson’s offense, he would be one weak link that Udoka would surely look to exploit.

4. Strus is loose

In the summer of 2019, the Celtics signed Max Strus, an undrafted free agent out of DePaul, to a two-way contract. They could have just kept him in that role, but ultimately gave that slot to Tacko Fall and gave Strus a partially guaranteed NBA deal to battle Javonte Green for the final roster spot. Green got the job and Strus was waived.

Less than three years later, the sharpshooter has turned into an essential piece for the Heat, bumping Robinson out of the rotation. He made 41 percent of his 3-pointers during the regular season, but that number has dipped to 35 in the playoffs.

The 6-5 wing has turned into a strong defender, too. During the postseason, the Heat have allowed just 94.1 points per 100 possessions with Strus on the court, and 116.1 while he sits.

Miami's Max Strus could play a big role in this series.Wilfredo Lee/Associated Press

Against Milwaukee, the Celtics were able to load up on Giannis Antetokounmpo and dare players such as Grayson Allen and Brook Lopez to hit shots. They didn’t. With Strus, Robinson, and Tyler Herro lurking for Miami, the focus will go back to the perimeter, particularly with drive-and-kicks and pick-and-pops that make Miami dangerous.

5. Robert Williams’s return

The Celtics center was sidelined for nearly a month after undergoing surgery to repair a torn meniscus in his left knee March 30. He returned midway through the Nets series, shook off some rust, and started to round back into form against Milwaukee before he missed the final four games of that series with a bone bruise.

Williams was cleared to return in Game 7 Sunday, but he did not play. Udoka said it was partly erring on the side of caution, but also that he was leery of disturbing the team’s rhythm. Also, the Celtics were looking for outside shooting to combat the Bucks’ defensive scheme

Against the Heat, though, Williams should be more essential, particularly to help as a last line of defense against slashers such as Butler and Herro. Also, Miami generally plays small, so there will be more lob threats for Williams on offense than there were against the Bucks’ hulking front line.

“It’s a little different coming into a new series as opposed to being injected into a Game 6 or 7,” Udoka said. “But he’s available and looking better every day.”

6. Kyle Lowry’s hamstring

The Heat point guard has been slowed by a hamstring injury he suffered in the opening-round win over the Hawks. He returned for Games 3 and 4 of the conference semifinals against the 76ers but then missed the final two games of that series.

On Monday, Lowry was ruled out for at least Game 1. Lowry did not practice Sunday, and hamstring injuries can be tricky, particularly for 36-year-old point guards who have appeared in more than 100 career playoff games.

Although Lowry played two games against Philadelphia, he clearly was not himself. He made 3 of 14 shots, committed five turnovers, and Miami lost both games.

What sort of impact could a healthy Kyle Lowry, center, have in this series?Matthew J Lee/Globe staff

The Heat surely would love to have the savvy, skilled, and experienced veteran on their side but will be aware of making sure he is not a detriment.

Bucks coach Mike Budenholzer said Sunday that, typically, some good fortune is needed to go on a title run. If Lowry misses this series, it would be the third time in a row that the Celtics’ opponent was missing an injured All-Star, following Ben Simmons and Khris Middleton.