Pryor, 22, took the place of Steve Delabar, who was optioned to Tacoma on Wednesday night. Pryor has been working as the closer in Tacoma, but pitching coach Carl Willis said the youngster will be used initially in middle innings as he breaks in.
"He's a power arm with a fastball that has been averaging 95 [mph] in Tacoma and has been up to 100, though you never really know about 100 until you see it for yourself," said Willis. "He's got a good slider and he's a strike thrower, but his command is still coming. We'll try to pick a spot here early on, middle of a game to get his feet wet and see what he's got and get him going."
To make room on the 40-man roster for Pryor -- the Mariners' No. 9 prospect entering the season, according to MLB.com -- the club placed veteran reliever George Sherrill on the 60-day disabled list. Sherrill is out for the season after undergoing Tommy John surgery on May 4, but had been on the 15-day DL.
Pryor, a fifth-round Draft pick in 2010, didn't allow a run in 12 innings over nine appearances for the Rainiers and recorded two saves after being promoted from Double-A Jackson. He allowed just five hits with seven walks and 15 strikeouts, and opponents were 0-for-16 against him with runners on base, including 0-for-6 with runners in scoring position.
Before his promotion to Tacoma, Pryor had posted a 1.13 ERA in Jackson with seven saves, allowing just two earned runs in 16 innings. Both earned runs came in his first appearance this season with Jackson on April 5 vs. Birmingham. Since then, he has not allowed an earned run in his past 27 innings, and his nine saves with Tacoma and Jackson are the most of any Mariners Minor Leaguer.
"I set a goal for myself to make it to the big leagues some time this year," Pryor said. "I didn't realize it would be this soon, but I'm excited about it and just feel like all the hard work has paid off."
Pryor knows he'll need to be more than just a hard thrower to get hitters out in the Majors, so he'll work his slider and changeup in with the heater.
"There's a few pitches I get away with, but guys at Triple-A and this level, if they see a pitch in the mid-90s two or three times in a row, they're going to time it up," he said. "That's what they get paid to do and they're pretty good at it."
The 6-foot-4, 245-pound Tennessee native split last season between Class A Advanced High Desert and Jackson. He has been strictly a relief pitcher in his three seasons in pro ball since being drafted out of Tennessee Tech, where he pitched one year after competing two years for Cleveland State in Tennessee.
He is 4-3 with 24 saves and a 2.87 ERA in 82 career Minor League relief appearances.