Moseley suffered the injury after popping up to Rockies shortstop Troy Tulowitzki. He immediately fell to the ground, clutching his left (non-throwing) shoulder.
He was replaced by reliever Cory Luebke to start the sixth inning.
The subluxation of the shoulder is something Moseley is familiar with, as it's happened to him in the past. He's scheduled for an MRI on Thursday.
"I guess it would be considered a dislocation, sublux in my left shoulder. I did [the same thing] back in '04 where it subluxed on me. It's been kind of a thing that I've strengthened and stayed on top of, would move occasionally just a little bit but never came out of place for that long," Moseley said.
In five innings Wednesday, Moseley allowed three earned runs on eight hits, including a solo home run to Todd Helton in the third inning. He struck out three and didn't walk a batter, but didn't figure in the decision in a game the Padres lost, 5-3, to the Rockies.
"I think I'm going to be OK. I got an MRI set up [Thursday]. Take a peek at it. I hope it doesn't affect anything with throwing. After it popped back in, I could move it around. I felt like I'd probably be able to throw, just swinging the bat, I'll probably have to be very, very careful," Moseley said.
"It's tough to describe. It's a real nervey feeling; everything is being stretched because the shoulder's not where it's supposed to be."
Moseley is scheduled to make his next start on Monday at Coors Field against these same Rockies.