WASHINGTON — The major issue with the 2019-20 Knicks is they don’t have an All-Star on the roster.

Technically, neither do the Wizards this season as shooting guard Bradley Beal was snubbed.

Before the Knicks faced the Wizards on Tuesday night, Washington coach Scott Brooks predicted Beal will be an All-NBA selection.

“He’s one of the top-10 players in the league,’’ Brooks said.

And he proved all that versus the Knicks, who blew a 16-point halftime lead as the Wizards rolled to a 122-115 victory at Capital One Arena. Beal racked up 40 points, made 4 of 10 3-pointers and was 14 of 16 from the line. He also added seven assists.

That will be president Leon Rose’s challenge in the offseason — adding a star to the roster.

RJ Barrett has potential, but had a lousy outing Tuesday and got banged up late. He finished with 16 points on 5 of 15 shooting (1 of 5 from 3). The rookie was hit in the face by Shabazz Napier, tumbled to the court and the blow drew blood with 1:52 left. Barrett stayed in the game.

Bradley Beal goes up for a shot during the Knicks' loss to the Wizards.
Bradley Beal goes up for a shot during the Knicks’ 122-115 loss to the Wizards.NBAE via Getty Images

The Knicks traded their No. 1 scoring option, Marcus Morris at the trade deadline for draft picks but he had never made an All-Star Game.

The Knicks dropped to 20-45 and continue their three-game road trip in Atlanta on Wednesday. There were a lot of Knicks fans in attendance Tuesday and they chanted “De-fense” with 2:30 left and the club down 10.

Beal drained two straight 3-pointers to bring the Wizards within 83-78 with 4:29 left in the third after the Knicks led 70-54 at halftime. The teams went into the fourth quarter tied at 87 after Beal drained another 3 with 25 seconds left.

The Knicks had no answers in the fourth quarter.

Frank Ntilikina had one of his best games, but mostly in the first half and surprisingly was not in the game most of the final period.

Ntilikina finished with 20 points and 10 assists in 29 minutes. Starting point guard Elfrid Payton had an off night (1 of 6, three points) but played a good chunk of the final session.

The Knicks got off to an awful start, falling behind 18-4 and rallied to take the lead at halftime after pouring in 39 points in the second quarter.

The Knicks surged on a 24-8 run to take a 28-26 lead with Ntilikina playing out of his mind. He was 3 of 3 from 3-point land before one of his shots changed to a 2-point goal 10 points later.

Before the game, interim coach Mike Miller praised Ntilikina’s recent success in getting to the basket.

Meanwhile, Bobby Portis, who finished last season with the Wizards, was a force, racking up 16 points of his 20 points in the first half.