Nelson said he's tolerating the pain well and will decide over the next few weeks whether he will have surgery now or hold off and attempt rehabilitation.
If he has surgery his season is probably over. If not, he'll likely still miss several weeks.
"Everybody's body is different," Nelson said before a promotional event at the University of Central Florida. "My body is obviously different than yours. You may take a year, I may take two weeks. I won't know any timetable right now. I just have to get treatment right now and see how I feel and where I'm at in a few weeks."
Nelson left the Magic's 105-95 loss to the Mavericks on Monday night in the third quarter after he stole the ball from Dallas center Erick Dampier, was fouled and hit the floor. Nelson came up bent over and clutching his right shoulder before heading to the locker room in pain.
He said Tuesday the tear occurred while he was ripping the ball away.
"I can't really say why it happened at this time," Nelson said. "Everything happens for a reason, I understand that. I think that's why my spirits are high."
The injury leaves the Southeast division-leading Magic (36-11) with a major hole.
Magic general manager Otis Smith said Tuesday he had "zero" regrets about not signing an extra point guard earlier. Now, he's hoping to fill the gap by any means possible -- including making a trade or signing a free agent.
"I don't think anything's off the table," Smith said. "We're actively pursuing [a deal], and have been since last night."
Nelson was having a career season, averaging 16.7 points and 5.4 assists per game. He was selected to his first All-Star Game and was to compete in the skills challenge in Phoenix.
The Magic host the Los Angeles Clippers on Wednesday night.
"It's a big blow for us," center Dwight Howard said after Monday night's loss. "I'm trying not to even think about it because he had been playing so well for us. It's a sad day for us all."
Nelson missed five games earlier this season with a right hip injury, and Orlando managed to go 4-1 behind Johnson.
A longer stretch against significantly better competition will provide a tougher test.
"We've done it before so we'll do whatever we have to do," Magic coach Stan Van Gundy said.
If the Magic can take any comfort in the loss, it's that they have time to regroup before the playoffs.
Orlando has a stranglehold on the Southeast division, beginning Tuesday with a nine-game lead over Atlanta. The Magic were three games behind Boston for the NBA's best record.
Still, Orlando's hopes for locking up home-court advantage in the East took a major hit.
"We don't change expectations at all," Lee said. "We can't say that we're losing because Jameer is out. We all have to step it up so that there's no drop off."