McCarthy had another flareup of pain in his right shoulder, a problem that has now caused him to miss time on four occasions this season. He was scratched from his start Saturday night, and Oakland placed him on the disabled list Sunday, retroactive to June 20.
Griffin was expected to be McCarthy's replacement when the latter was scratched, given that the rookie last pitched for the River Cats on June 19, the same day that McCarthy pitched for the A's. Drafted by Oakland in the 13th round in 2010 out of the University of San Diego, Griffin has pitched well this season over two Minor League levels, having started the year at Double-A Midland.
The 24-year-old is 6-3 with a 2.66 ERA overall and has given up just five runs in 29 innings in his last four starts for Sacramento.
"When this situation came up, he was the guy that was recommended [by the player development staff]," said A's manager Bob Melvin before Sunday's game, Griffin's Major League debut. "When you look at his numbers, he's pitched very well. He's supposed to be a very mature kid and they feel like he's up to the task here today. Therefore, we'll take a look."
Fellow recent callup Derek Norris caught Griffin at Triple-A, and Melvin put him in Sunday's lineup at catcher because of his familiarity with the rookie. Norris said that Griffin locates the ball well and pitches to contact. He has a four-pitch mix but is especially effective with his fastball-changeup combination, in Norris's eyes.
"The way he was pitching, it was only a matter of time before he got a chance to come up here and pitch, but any of the guys we got down there, whenever they get their chance, they're going to come up and do good things," Norris said. "He's done a great job, and hopefully he can just continue what he's doing down there up here."
To make room for Griffin on the 40-man roster, Sacramento reliever Danny Farquhar was designated for assignment.
Ben Estes is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.