The Lakers’ existence in the NBA food chain actually didn’t look that bad, despite LeBron James sitting on the bench with a walking boot on his lower right leg.

Anthony Davis was on his way to a ridiculous game and the Lakers were beating the Memphis Grizzlies at halftime Tuesday at Memphis.

Then came the third quarter. More specifically, Ja Morant happened.

The Memphis guard scored 28 points in the third quarter, the most by any NBA player in a quarter this season, as the Lakers saw their upset chances slowly fade.

Morant finished with 39 points, 10 assists and 10 rebounds as the Grizzlies pulled away for a 121-109 victory.

Morant had only six points in the first half on dreary three-for-14 shooting. That changed quickly. His outburst pushed the Grizzlies from a three-point halftime deficit to a 93-84 lead going into the fourth quarter.

It didn’t help that James sat out because of an injured right foot he sustained two days earlier against Dallas. He’s doubtful to play Wednesday at Oklahoma City, Lakers Coach Darvin Ham said.

The Lakers didn’t provide a specific update on James other than Ham saying James continued to undergo a “diagnostic” process with doctors to determine the next steps medically. An ESPN report said James would be out at least two weeks before being evaluated again because of the unspecified injury.

“We have more than enough in my opinion to still win basketball games,” Davis said. “We have to. [LeBron’s] not coming back any time soon.”

James was hurt when he drove to the basket Sunday, felt a pop in his right foot and crumpled to the ground late in the third quarter. He remained down on the court for a while but didn’t head to the locker room and scored 11 points in the fourth quarter of the Lakers’ dramatic come-from-behind victory against Dallas.

He wasn’t the only sidelined Lakers player against Memphis; D’Angelo Russell missed his second consecutive game because of a sprained ankle.

Despite it all, the Lakers led at halftime, 49-46, thanks to inspired play from Davis and a four-point play from Austin Reaves after he was fouled while drilling a three-pointer.

Davis was everywhere in the first half, collecting eight points, 10 rebounds and four blocked shots while evoking images of his dominant play earlier this season before he was sidelined by a stress fracture in his foot.

There were some trouble spots for the Lakers beyond stopping Morant. They were punished by the basket and handily outscored in the paint, 86-48. They also coughed up the ball a season-high 26 times, leading to a generous 41 points for Memphis.

“Indecisive. Indecision,” Davis said. “They are a physical team and they got into us a little bit. We were just a little hesitant, whether it was a drive, a shot. We’ve just got to take care of the ball.”

He added later, “The turnovers are what killed us tonight.”

Lonnie Walker IV scored 21 points and Reaves added 17 as the Lakers (29-33) failed to move two games below .500 for the first time since Jan. 7.

“You turn the ball over. It’s hard to get your defense set,” Ham said. “You can see their 33 points in transition. It was a cause-and-effect with our turnovers.”

Xavier Tillman had 18 points and 11 rebounds for Memphis (37-23), which had lost 10 of its last 15 games before Tuesday.