CLEVELAND — Boston Celtics coach Brad Stevens thought he was watching a videogame as the Cavaliers made three-point baskets with ease and regularity during the first half Sunday night at Quicken Loans Arena.

“It was like, ‘oh, my gosh,’ this is a little bit unbelievable,” Stevens said of the Cavaliers’ 14-of-22 shooting from behind the arc in the first half.

As the Celtics began to mount a third-quarter comeback, Cavaliers coach Tyronn Lue needed to take the Xbox controller from the clutches of his long-shot-happy club. Cleveland’s reliance on attempts from distance played a part in its second-half collapse and stunning 111-108 loss in Game 3 of the Eastern Conference finals.

The series resumes tonight with the Cavs leading two games to one after their 13-game playoff win streak dating to last season ended in shocking fashion.

The Cavs converted just four baskets in the lane once they built a 21-point lead midway through the third quarter. Meanwhile, they made just 2 of 17 three-point attempts in the second half. Lue knows his team needs better balance heading into Game 4.

“I thought we fell in love with the three a little bit too much,” Lue said Monday. “In the second half, I thought we were seeking the three instead of attacking. I thought we had opportunities to attack and play with pace and get downhill, but we didn't really push it and play with that speed and try to attack offensively.”

No player was more guilty than LeBron James, who finished with just 11 points on 4-of-13 shooting. One of the game’s most lethal penetrators, James was credited with just five field-goal attempts within 10 feet of the rim.

James’ confidence in Game 3 was questioned by teammate and friend J.R. Smith.

“He's got to be aggressive, get downhill, play like he's been playing, play confident,” Smith said Monday. “That's what I always think, when people of his stature or people like him, you've got to play confident the whole night and play aggressive.”

James was content to let Kevin Love (28 points) and Kyrie Irving (29 points) connect from long range in the first half as they combined for 11-of-14 shooting from behind the arc, leading the Cavaliers to a 16-point lead.

The four-time NBA Most Valuable Player figures to be in attack mode from the outset tonight. James and Irving are the club’s best penetrators on a team with an array of three-point-shooting options such as Love, Kyle Korver, Smith and Channing Frye. The Cavaliers lead the postseason in three-point shooting percentage (43.0).

Maybe the Cavaliers expected the Celtics to roll over after two lopsided wins in Boston and playing without All-Star guard Isaiah Thomas. But the Celtics already have rallied from a 2-0 series deficit against Chicago in the opening round after dropping the first two games at home.

Boston finished with more three-point baskets (18) than Cleveland (16) Sunday night, but it needed the weapon to reduce the large second-half deficit.

After cruising to 10 wins to start the playoffs, James hopes Sunday’s loss benefits the Cavaliers.

“I feel like you have to have some type of adversity in order to be successful," James said after the game. "If it was going to happen, let it happen now. Let us regroup. Let us regroup, and all the narrative and everything that was going on, let's regroup, and let's get back to playing desperate basketball. … We've got to be a lot better, for sure."

Taking a few more shots in the lane might be a good place to start.