LeBron James dribbled out the final 20 seconds while players embraced as the Cavaliers completed a sweep of the Celtics.
It may have been the calmest, most congenial 20 seconds of a physical game that left two players with potentially serious injuries and Cleveland wondering if Kevin Love would be ready for the next round.
One thing is certain: Love was angry after Cleveland beat Boston 101-93, a game he left midway through the first quarter Sunday with a dislocated left shoulder.
Kelly Olynyk had his right arm entangled with Love's left arm - a move Love called "bush league" and intentional- as both went for a loose ball. Love grabbed his left shoulder and ran immediately to his locker room. Boston coach Brad Stevens said deliberately hurting a player is not in Olynyk's personality.
James, who led Cleveland with 27 points, said he's "seen a lot of tie-ups in my day, but that one looked different."
Later, Boston's Jae Crowder was involved in two physical plays. First, he was shoved by Kendrick Perkins and both drew technical fouls. Then he left the game with a sprained left knee when he was knocked down as J.R. Smith swung his arm backward while jostling for a rebound early in the third quarter.
Smith was ejected and faces possible suspension to start the second round. He was suspended a game in the 2013 playoffs while playing for the Knicks after elbowing Jason Terry during a victory over the Celtics.
"Things got a little chippy," Cleveland's Kyrie Irving said. "Game 4 was the most physical game I have ever played in."
But Boston's Isaiah Thomas didn't think it was anything to complain about.
"We are all men here. We don't need to cry," the 5-foot-9 Thomas said. "It's playoff basketball. You need to move forward."
That's just what the Cavaliers are doing after winning their first playoff series since 2010, before James left for Miami. Next up is the winner of the Chicago-Milwaukee series. The Bulls lead 3-1.
Irving had 24 points for Cleveland and Iman Shumpert added 15.
Thomas and Jared Sullinger had 21 points apiece for Boston.
The Cavaliers led 57-36 at halftime even though James missed eight of 12 shots and Love missed most of the half.
The team said Love would return to Cleveland and receive additional examination, imaging and evaluation at Cleveland Clinic Sports Health over the next 24 hours before his status is updated.
The Celtics were competitive for most of the series, losing the last three games by eight points each.
""I like our progress but I like to win," Boston coach Brad Stevens said. "So I'm disappointed."
The Celtics outscored the Cavaliers 25-13 in the third quarter to cut the lead to 70-61. And when Smith was ejected, Boston became more aggressive, scoring the next six points, while Cleveland missed 16 of 20 shots in the period.
The Cavaliers led 99-89 with 44 seconds left, but the Celtics didn't give up. Thomas hit a layup then, while out of bounds, grabbed James, who was trying to inbound the ball. No call was made - Cleveland coach David Blatt said it should have been a technical - and the Cavaliers committed a foul when the ball was put in play.
Avery Bradley sank the two free throws to cut the lead to six before the ball went out of bounds off Irving. But Gigi Datome missed a 3-pointer before Irving was fouled and made two shots.
The Cavaliers won their first series since beating the Bulls in the opening round in 2010 before losing to Boston. James left for Miami two months later.
The sweep was the Cavaliers' first since 2009, when they did it against Detroit and Atlanta before losing to Orlando in six games in the Eastern Conference finals.
"We have some vets but we're a young team together," James said. "The Celtics gave us the test that we needed."
For the Celtics, it was a swift end to a rebuilding season that lasted longer than expected. That followed a regular season in which they went a surprising 40-42, a 15-win increase over the previous season. And they have reason for optimism with four draft picks this year and the potential of four first-rounders next year.