The Mariners aren't setting any exact timeline, but Paxton and Taijuan Walker each will need a couple bullpen sessions, then likely a pair of simulated games before going out on Minor League rehab stints.
Walker will also throw a bullpen session Sunday, his first since being shut down with a recurring shoulder issue in mid-April.
"I really have no idea when I'll be back exactly," Paxton said. "But as long as I'm feeling good, it shouldn't be too far off. If I could decide, I'd be starting tomorrow. But I'm not allowed to do that."
For now, both youngsters will just follow trainer's orders, which means throwing in the Safeco Field bullpen for now.
"I felt awesome," Paxton said. "It was nice to get back up on the mound, that's for sure. It has been a little while, so it was exciting to get back up there and throw some pitches."
Paxton was limited to fastballs and changeups and didn't throw full out, as instructed.
"Right now I'm trying to get my timing back and just be smooth," he said. "They told me not to go full speed. Obviously it's not game-like right now, we're just trying to make sure it feels good and everything and it did. It was just nice and easy, smooth arm action."
Pitching coach Rick Waits said Sunday will be a big day with Paxton and Walker both taking the mound prior to that afternoon's series finale with the Royals.
"Taijuan looks great [playing catch so far]," Waits said. "He's just nice and loose and excited about getting on the mound, too."
Greg Johns is a reporter for MLB.com. Follow him on Twitter @GregJohnsMLB as well as his Mariners Musings blog. This story was not subject to the approval of Major League Baseball or its clubs.