Injuries are having a major impact on the NBA playoffs.

A tweak, turn or strain to this or that has sidelined or limited players from All-Stars to reserves — and that has influenced the early outcomes of Round 2.

After Jaylen Brown strained his right hamstring in Boston's Game 7 win over Milwaukee, he all but begged the Celtics doctors and trainers to let him suit up for the start of their Eastern Conference semifinal matchup with Philadelphia.

Boston managed to win without him in its 117-101 victory over the sluggish 76ers in Game 1 Monday night, thanks to career nights by Al Horford, Terry Rozier and rookie Jayson Tatum.

But despite two days or rest and treatment, coach Brad Stevens said Brown is "very doubtful" for Game 2 on Thursday night.

"The bottom line is with this hamstring injury is it's not terrible. Not a long-term thing. It shouldn't linger if he comes back at the right time," Stevens said.

If Brown can't go for Game 2, it will again put stress on a Celtics rotation that just recently got back Marcus Smart from a right thumb surgery.

Fred VanVleet appeared to tweak his right shoulder in the second half of the Raptors' 113-112 overtime loss to Cleveland in Game 1 of their series Tuesday night. He missed most of Toronto's first-round series against Washington with shoulder problems, but the Raptors still turned to him with the game on the line against the Cavaliers. VanVleet missed what would have been a go-ahead 3-pointer in the waning moments of regulation and another in the extra frame.

"I wish I wasn't hurt," he said, "but I'm not looking for any excuses."

Elsewhere in the league, the return of some players and absence of others has been just as noticeable.

Stephen Curry, who sat out all of Golden State's first-round series win over San Antonio with a sprained ligament in his left knee, gave the Warriors a major lift in his return for Game 2 of the Golden State's semifinal matchup with the Pelicans on Tuesday night.

Ricky Rubio missed the Jazz's series-opening loss against Houston on Sunday with a left hamstring injury and is out indefinitely. The Rockets' Luc Mbah a Moute returned in Game 1 from the dislocated right shoulder he sustained last month. Houston originally thought he's be out a full month, but he came back ahead of schedule and didn't show any lingering effects from the injury in 21 minutes of action.

A closer look at Thursday's games:

CAVALIERS AT RAPTORS

Cavaliers lead 1-0. Game 2, 6 p.m. EDT, ESPN.

NEED TO KNOW: The Raptors have lost seven straight playoff games against the Cavaliers, dating to the 2016 Eastern Conference finals, and blew a chance to take a lead in the series by coughing up a 10-point lead in the fourth quarter of Game 1 . The Raptors missed four potential game-winning shots at the end of regulation, and a wide-open 3 by VanVleet late in overtime.

KEEP AN EYE ON: Raptors center Jonas Valanciunas. He had 21 points and 21 rebounds in Game 1 and shot 7 for 19, but missed five of six attempts in the fourth. On Wednesday, Cavs coach Tyronn Lue said he can live with Valanciunas getting looks in the post if it means fewer touches for Kyle Lowry and DeMar DeRozan, and fewer 3-point attempts by the Raptors.

INJURY UPDATE: While VanVleet acknowledged he's still dealing with discomfort in his shoulder, he plans to play through it for now.

PRESSURE IS ON: The Raptors. The top-seeded team in the East has already surrendered home court advantage to its playoff nemesis and is 0-5 all-time on the road against Cleveland in the postseason. If Toronto can't even this series before it shifts to Ohio, it might not be coming back across the border for Game 5.

76ERS AT CELTICS

Celtics lead 1-0. Game 2, 8:30 p.m. EDT, TNT.

NEED TO KNOW: The Celtics negated the athleticism of the 76ers in Game 1 by knocking down 17 3-pointers. Before the big scoring nights by Rozier (29 points), Tatum (28 points) and Horford (26 points), the Celtics hadn't had three players score 25 or more points in a playoff game since 2009.

KEEP AN EYE ON: 76ers C Joel Embiid. He had 31 points and 12 rebounds in Game 1, becoming the first Philadelphia player to register 30 points and 10 rebounds in a playoff game since Allen Iverson in 2001. But he said the focus will be on defense in Game 2. "We didn't stick to the game plan," he said. "There's a lot of stuff we can definitely correct."

INJURY UPDATE: Smart said Wednesday that his thumb remained "a little sore" after Game 1 but added "I'm good to go" for Game 2.

PRESSURE IS ON: The 76ers. They entered the series on six days of rest but were doomed by a slow start in Game 1. This young group mostly cruised over the final three games last series against Miami. Being down 0-2 with its home court to defend is a lot to ask against a Celtics team playing with a lot of confidence.

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AP Freelance Writer Ian Harrison contributed to this report from Toronto.