BOSTON — It took 10 games and halfway through the third round of the NBA playoffs before the Cleveland Cavaliers finally encountered their first true dose of resistance this postseason.

After cruising to a 2-0 Eastern Conference finals lead over Boston, the Cavs were humbled at home in a Game 3 loss, and needed a 42-point night from Kyrie Irving to battle back from a 16-point hole and win Game 4.

The chatter about an NBA Finals’ matchup of two teams with unblemished playoff records is gone, but the challenge from the Celtics has sharpened the focus of the defending champs. Cleveland is expecting another unflinching effort in Game 5 from a Celtics team that isn’t backing down despite facing a 3-1 deficit in the series.

“The closeout game is always the hardest.and Boston is going to make it even harder,” said LeBron James, who rebounded from a playoff-low 11 points in Game 3 to score 34 in Game 4.