Pryor threw a 1-2-3 eighth inning and was hitting 97-98 mph with his fastball as he struck out Eric Chavez and Russell Martin and got Ichiro Suzuki to ground out.
The 23-year-old pitched six games in June for the Mariners before straining his groin muscle while making a play at first base and going on the 15-day disabled list. He then spent several weeks back in Triple-A once he recovered, but was brought back up to Seattle after Brandon League and Steve Delabar were traded Tuesday.
"Pryor was really good yesterday," manager Eric Wedge said prior to Saturday's game. "I wanted to get him in there because he'll be pitching meaningful innings for us, but he hadn't pitched in five or six days."
With all of seven games now in the bigs, Pryor is still a guy Capps is turning to for advice since they played together earlier this year in Double-A Jackson.
"Everyone is a veteran to me," Capps said with a grin.
"I don't know about that, but I try to look out for him, and everybody else is, too," Pryor said. "Everybody is excited he's here. It's going to be good. We had a month together in Jackson and then 3-4 days in Triple-A. We get along real well, play catch together, work out together. It's a good competition with each other. We push each other."
Capps became just the second player from the 2011 Draft to make his MLB debut when he pitched a third of an inning Friday, giving up a single, a walk and two runs while flashing his 100-mph fastball. Capps, who'll turn 22 on Tuesday, joins D-backs pitcher Trevor Bauer as the only players from last year's Draft to appear in the Majors so far.
"I don't know how many pitchers in the history of the game have had their first pitch at 100 mph," said Wedge. "But there can't be too many of them. And hey, it wasn't too traumatic. He got to face three hitters and got an out, so it was good. Your big league debut in Yankee Stadium? Not a bad day."