Chris Brown, Rihanna

Chris Brown's cancelled appearance at The Grammys was only the first of many.

The R&B star, arrested Sunday in a felony battery case, has also pulled out of a scheduled appearance at Sunday's 2009 NBA All-Star Game. The basketball fanatic had been expected to announce the players with Shaquille O'Neal before tip-off at Phoenix's US Airways Center. Brown also dropped out of playing in Friday's All-Star Celebrity Game.

Rihanna, who the Los Angeles Times has identified as the accuser in the case, postponed a sold-out show scheduled for Friday in Kuala Lumpur.

"We sincerely regret this unavoidable shift in schedule and apologize to the fans for any inconvenience caused," Pineapple Concerts managing director Razman Razali said in a statement. A replacement date will be announced within two weeks, Razali said.

Rihanna was discharged from Los Angeles' Cedars-Sinai Medical Center Monday night, a source close to the investigation told E! News. A decoy distracted photographers while the singer was escorted out the back door, the site said. Rihanna's rep did not immediately respond to phone calls and e-mails.

Brown and Rihanna were reportedly in good spirits early Sunday as they left Clive Davis' pre-Grammy party. But police responded to a call soon after in which a woman who has not been identified said Brown attacked her during an argument. The woman suffered visible injuries, police said. Brown was not on the scene when officers arrived.

Los Angeles District Attorney's Office spokeswoman Jane Robison told TVGuide.com that charges have not been filed against Brown and that the LAPD hasn't presented its case. "They have 30 days to investigate, so there's not a rush," she said.

TVGuide.com's calls to Brown's attorney, Mark Geragos, have not been returned. Rapper T.I. said he has talked to Brown, and that he's "still the same old Chris."

Rihanna's former tour mate, Kanye West, said he would do anything he could to help her.

"She has the potential to be the greatest artist of all time and, in that sense, I feel like that's my baby sis and I would do any and everything to help her in any situation," he told E! News' Ryan Seacrest. "I don't want to speak more into the specifics with that situation, but all I'll say is it's just so devastating.

"I feel like, just as a person, I don't care how famous she is or even if she just worked at McDonald's, that should never happen. It should never come to that place."