Boston Celtics swingman Mickael Pietrus is taken off the court on a stretcher after a scary fall in Philadelphia. (Matt Slocum/AP)

Pietrus was driving to the basket when he collided with 76ers point guard Lou Williams and crashed to the floor, landing hard on his lower back and immediately clutching his neck. He was seen convulsing, vomiting and spitting up blood immediately after the fall.

But after receiving an X-ray, CT-scan and MRI, Pietrus remained in Philadelphia overnight, but was not forced to stay in the hospital overnight. The Celtics reported Pietrus sustained a concussion. He will be re-evaluated today.

Pietrus update: Suffered a “questionable closed head injury” (concussion). Had X-ray, CT scan and will get MRI. Staying overnight in Philly.

— Boston Celtics (@celtics) March 24, 2012

“It looked awful,” Celtics Coach Doc Rivers said. “I saw it immediately. I didn’t think he hit his head, but I wasn’t sure. I just saw his neck snap, and so you knew that was bad. And obviously he was throwing up on the floor, so that’s not very good either. I mean, wow, that was tough. I think that was tough for all of us to see.”

The Celtics, who led by 10 points before Pietrus’s injury, would have moved past Philadelphia and into first place with a win, but the 76ers rallied for a 99-86 win. After the game, Boston’s focus was on its fallen teammate.

“It’s always tough when you see your fellow brother, NBA player — regardless of who it is,” Celtics guard Paul Pierce said. “When you catch somebody laying there on the ground and not moving and you get carried off the floor on a stretcher, it’s tough.

“Those are things that can be career-ending type of things. We just hope he’s able to make a speedy recovery.”

More NBA coverage from Washington Post Sports:

Pietrus hospitalized; 76ers beat Celtics as Collins wins No. 400

Bolton’s Fabrice Muamba improving after in-game heart attack

Miami Heat, LeBron James, don hoodies for Trayvon Martin