Manaea, 25, tends to throw his fastball anywhere from 90-95 miles per hour, averaging 92.5 in his first four starts of the season. It was alarming that after two innings, he was sitting 87-89 miles per hour, ony topping 90 a handful of times. He was taken out of the game after just 34 pitches in two innings.
"(Sean) had tightness in the top of his shoulder and his velocity was down, so it didn't make sense to make him keep pitching," said A's manager, Bob Melvin. "We won't know anything for probably a day or two."
Once considered one of the top prospects in baseball, Manaea fell to the latter stages of the first round in 2013 due to concerns about his shoulder. In 2014, while in Spring Training with the Kansas City Royals, he had a similar situation occur, but it was never a lingering concern.
"It was kind of a little sharp pain, nothing serious," said Manaea. "I've dealt with it before. To me I'm not really worried about it."
Prior to the game, Manaea did feel the tightness, but thought little of it.
"I felt it a little bit in the bullpen and just thought it was one of those days where it took me a little longer to warm up," Manaea said. "It's just really unfortunate."
The A's rotation has been hit with injuries already this season. All-Star pitcher, Sonny Gray, has missed the start of the season with a lat strain. Kendall Graveman is expected back soon from a right shoulder strain. Chris Bassitt is in the final stages of recovering from Tommy John surgery and is expected back in June. Daniel Mengden underwent foot surgery prior to Spring Training, and has no time table for a return.
"It seems kind of like a revolving door right now," Melvin said. "Hopefully this isn't a long term problem for Sean."