ORLANDO, Fla. — The Orlando Magic is expected to find out Tuesday if their merry bandwagon has lost a wheel, jeopardizing their drive to title contention this season.

All-star point guard Jameer Nelson dislocated his right shoulder in a 105-95 loss Monday night to the Dallas Mavericks and will undergo an MRI to determine the injury's severity.

Just how long Nelson will be out is the question, but the team seemed to be braced for him to miss weeks, not days. If surgery is required, he will be lost for the season.

According to WebMD.com, patients with dislocated shoulders not requiring surgery can need anywhere from three to 12 weeks to recover, depending on the severity.

"We don't even know how bad it is right now," said Nelson, whose right arm was in a sling. "We just know it's dislocated. That doesn't mean anything right now until we get an MRI and see how it goes after that."

If Nelson is out for significant time, the club likely will have to sign another point guard or trade for one.

Magic forward Rashard Lewis said he separated a shoulder while playing for Seattle and missed two weeks. Miami Heat guard Dwyane Wade had a dislocated shoulder in 2007, missed 23 games and decided to have offseason surgery.

"It's a big blow for us," center Dwight Howard said of Nelson's injury. "I'm trying not to think about it because he's been playing so well. It's a sad day for all of us."

The Magic (36-11), who played one of their worst games of the season against the Mavs (28-19), do not have a third point guard behind Nelson and backup Anthony Johnson. They did not replace Mike Wilks after Wilks suffered a season-ending knee injury in the preseason, leaning on Hedo Turkoglu as a playmaker.

Nelson said he had "no idea" how he was injured early in the third period, but replays showed him recoiling in pain after trying to steal a ball from Mavs center Erick Dampier under the basket. He reached into Dampier with his right arm, jarred the ball loose, but then collapsed seconds later.

Nelson said he sensed the shoulder might have popped out, and he jogged off the floor in an awkward bent-over fashion. He did not return to the game and was replaced by Johnson, who will assume the starting job until further notice.

"I don't know when it happened and how it happened," Nelson said. "I just know I felt a little pain and then, obviously, I saw it hanging out. I didn't hurt my legs, so I just ran down to the end of the court.

"I remember I fell on the floor, but I don't even remember hitting him. He may have grabbed my arm or whatever, but I'm quite sure he didn't do it intentionally to pop my shoulder out."

Nelson is having a career season, averaging 17 points and 5.5 assists per game. He missed five games earlier this season with a right hip injury, but the Magic managed to go 4-1 behind Johnson.

The Mavs were getting the better of the Magic long before Nelson's exit.

Dallas broke away in the third period behind Dirk Nowitzki and Jason Terry, eventually leading by as many as 20 points. "That was pretty simple," Coach Stan Van Gundy said. "We weren't able to stop them and we couldn't score on them."

Howard scored 35 points and grabbed 11 rebounds, but he didn't have enough help to prevent the Mavs from snapping the Magic's three-game winning streak. The most accurate 3-point-shooting team in the league, the Magic were just 3 of 20.

But the loss of Nelson was more significant than the loss to the Mavs.