Paxton said he was ready for the next step, a Minor League rehab stint of his own. If he made two Minor League starts and all went well, he would be ready to rejoin the Mariners in early June.
Walker is slightly behind Paxton's schedule, and the club will be extra-cautious with the 21-year-old after a spring-long issue with his shoulder, though he looked strong Tuesday and finished his session by blowing a sizzling fastball past Cole Gillespie that popped the mitt of catcher John Buck.
"Everything felt good," said Walker, who is rated the No. 6 prospect in baseball by MLB.com and No. 1 in the Mariners' system. "My mechanics felt good, everything was in sync, my balance point was good. One of the biggest things I've been working on was finishing more to keep stress off my arm, and I think I did that pretty well."
Walker now exaggerates his throwing motion at the end of his pitches to get more extension, and he said the results had been encouraging. He was also happy with his off-speed pitches Tuesday.
"I threw a couple curves that kind of hung up, but for the most part it was down," he said. "I threw a couple really sharp ones. That's something I've been working on a lot and could be a huge pitch for me."
Paxton, who went 2-0 with a 2.25 ERA in two starts before going on the DL on April 8, was equally positive about what he hoped was a penultimate step before returning to game action.
"It was a step forward with my command and making pitches," the 25-year-old lefty said. "I feel pretty close. I think the next step is a rehab start, and I feel I'm ready for it, ready to get in some games and get back. It's time to step it up and get back into that game mode, so I was starting to let things go."
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.