Jaylen Brown did not want to make excuses but acknowledged "everything was going wrong for us" after the Boston Celtics' upset loss at the Washington Wizards.

The Celtics had the opportunity to close to within one win of the Milwaukee Bucks and the number one seed in the East on Wednesday.

Instead, they went down 130-111 to a Wizards team missing Bradley Beal and Kyle Kuzma.

One of the Celtics' team buses was stuck in traffic for around an hour before the game, and although Boston recovered to make a solid start, it was the first sign of the troublesome night that was to come.

"Tonight it just seemed like everything was going right for Washington; everything was going wrong for us," Brown said.

"On top of all the stuff that was happening before the game... but I'm not one to make no excuses."

The Celtics had recovered from a run of three straight defeats in early March to win seven of the next nine before visiting the Wizards.

While Boston are now 2.5 games back, Brown knows they cannot afford this one-off defeat to become part of a slump.

After the Bucks play the Indiana Pacers on Wednesday, they welcome the Celtics to Wisconsin the following night.

"Games like this are not supposed to happen. You're supposed to win," Brown said. "But it's over with now, nothing we can do about it.

"I'm not concerned, because the way my brain works is you have just got to look forward to what's next.

"You don't want one bad night to turn into three bad nights or a bad week. Nobody wants to see that. We don't want to see that, so you don't harp on it.

"Obviously, we dropped the ball. But now you have just got to refocus and get ready for the next one."