The decision, manager Bob Geren said, was strictly based on performance. Blevins allowed 24 base runners in just 13 2/3 innings of work for the A's this year, while Magnuson surrendered just eight hits next to 18 strikeouts with nine walks over 17 1/3 frames in Sacramento.
"Magnuson was throwing the ball extremely well down there," Geren said. "We got great reports about him, and he's replacing a guy that struggled."
The 25-year-old Magnuson, acquired this offseason in the Rajai Davis trade, is embarking on his first Major League stint. Owner of a fastball, cutter and slider, he left big league camp with the A's this year and entered Triple-A with work to be done, particularly on his breaking ball and command.
"He's eager to learn," Geren said. "Week to week, we kept getting reports on how well he was throwing, and we're happy with his progress."
"The ball was coming out good," Magnuson said. "I just gotta attack. I was talking to Joey Devine. He said the biggest thing is to be aggressive, so that's what I'm going to try to do -- throw strikes."
Magnuson, the 56th overall Draft pick in 2007, will fill the middle-relief role held by Blevins, though Geren noted he'll stay away from placing the rookie in a high-pressure situation for a few days. He last pitched Monday, when he logged two scoreless innings against Colorado Springs.
The wide-eyed hurler first received news of his promotion on Tuesday night in Memphis, where the River Cats just began an eight-game road trip. He was called into manager Darren Bush's office and was ragged for his unavailability.
"I was flustered because I had been down in the bullpen the whole time," Magnuson said. "He said, 'That sort of stuff doesn't fly here, or in the big leagues tomorrow.'"
Magnuson, a Vancouver native, immediately woke his parents with the news. Unfortunately, it was too late for them to get to Texas for Oakland's series finale because of the afternoon start time, but he mentioned they "were really excited for me."
The 6-foot-7 hurler reveled in his first-class flight experience, noting his ability to stretch out was the only reason why he was able to rest his nerves and get some sleep -- though not much.
Blevins was rightfully disappointed but understanding of the move, particularly after posting a 4.61 ERA in 14 relief appearances. He had walked 12 batters and surrendered 12 hits -- including two home runs -- while striking out 13.
"I'm not as happy with the way things turned out numbers-wise," Blevins said. "I'm OK with my performance. I know I always strive to be better, but I'm a big leaguer. I belong in the big leagues, so of course I'm going to be upset not being able to do my job."
The southpaw hopes to find consistent work in Sacramento, which he wasn't always afforded on an A's team that sees its starters go deep into games on a near daily basis.
"Do I want to pitch more often? Of course I do," Blevins said. "Do I understand why I'm not? Absolutely. Our starters go so deep into games, and guys in the back of the bullpen make a lot of money for a reason. So the opportunities are few and far between, but as a competitor, of course I want to pitch more often."
Geren, who hopes to see Blevins improve his command, understands the notion of inconsistent work but said, "That's the way the bullpen is. That's the life of a reliever."