Boston Celtics guard Marcus Smart got into a spat with assistant coach Jerome Allen during a fourth-quarter timeout in Tuesday's 123-108 loss to the Washington Wizards. It was pretty heated. Here's video of the incident:

The cause of Smart's frustration? The Celtics were losing, and he wanted to be on the court. Here's the explanation from coach Brad Stevens and Smart, via masslive.com's Jay King:

"He just wanted to go back in. And he had played 12 (straight) minutes or whatever so he wasn't going to go back in. He wanted to go back in," Stevens said. "He wanted to go back in badly."

...

"Of course I wanted to go back in, like everybody else, to play it out and give everything that I have -- leave it on the court," said Smart, who retreated to the locker room after the dispute. "We had different opinions on that."

He added: "Just coaches and players that are real passionate about the game. And they're losing and having different opinions about certain things in the game."

Directly before the timeout and the argument, Smart tried to check himself back into the game. The coaching staff did not approve of this. You can see Stevens following Smart to the scorer's table here:

After the game, Smart apologized for his "childish and unprofessional" behavior with a tweet:

Smart is known as an intense competitor, and he's clearly not having a lot of fun right now. Boston has lost its past three games, with Smart shooting 10 for 34 during the streak. It's not about to get any easier, either -- the Celtics will host the Houston Rockets on a back-to-back on Wednesday, and Smart will likely be the primary defender against James Harden.

Add CBS Sports on Google