Ahead of a must-win game for the Celtics, Globe sports columnist Chad Finn explains what’s gone wrong for the team.

Jayson Tatum’s potentially serious lower left leg injury cast a pall over the second round. Tatum collapsed to the ground in the fourth quarter of the Celtics’ Game 4 loss to the New York Knicks and had to be carried off the court after he was writhing in pain and grabbing at the back of his ankle.

Jayson Tatum gets shaken up after a foul by Josh Hart causes the Celtics star to fall hard on his hand vs. the Knicks.

If the Celtics extend their season by beating the visiting New York Knicks in Game 5 of the Eastern Conference semifinals Wednesday night, they will do so without leading scorer Jayson Tatum.

Jalen Brunson scores 39 points as the New York Knicks leave the Boston Celtics on the brink of NBA play-off elimination.