OAKLAND -- The A's will be without reliever Blake Treinen for the rest of the regular season, and likely the postseason as well.
An MRI revealed a stress reaction in Treinen's back, an injury he expects to sideline him for at least four weeks.
"They told me it's typically a 4-6 week type recovery process just to make sure it's all gone," Treinen told NBC Sports California. "So if I'm symptom-free for two weeks with my activities and then we try to push it a little bit and nothing happens, then I could be good for a (playoff) series. I don't really know. My biggest thing is just trying to keep my head down and focus on strengthening myself in the weight room in the right areas without aggravating it."
Treinen, 31, says his back issues intensified a few weeks ago. The right-hander initially thought he could pitch through the discomfort, but the MRI made it clear he couldn't.
"It's one thing to have aches and pains and then be able to get some type of soft-tissue work," Treinen said. "That's what we were doing, but nothing was relieved."
After an All-Star season in 2018, Treinen has struggled this year, going 6-5 with a 4.91 ERA, the worst of his career. Still, his injury leaves the A's bullpen a man down, which is why starting pitcher Chris Bassitt volunteered to help out in relief.
"I just said, 'Listen, if you guys need me out of the bullpen in between starts or whatever it is, I'll do it,'" Bassitt said. "I've done it before, so it's not a big deal for me."
On Wednesday, Bassitt began to warm up in the 11th inning of the A's 1-0 win over the Royals, preparing to pitch the 12th. That didn't end up being necessary, but the right-hander's presence in the pen should certainly help Oakland moving forward.
Said A's manager Bob Melvin: "The way guys are pitching -- (Sean) Manaea back in the rotation -- we need some more depth in the bullpen and Bassitt was the first one that volunteered to do it and was all for it. So he's going to do whatever he can to help the team."
Oakland has been employing a six-man starting rotation, with Manaea, Bassitt, Homer Bailey, Tanner Roark, Brett Anderson, and Mike Fiers all getting regular starts. That depth is what allowed this move to the pen.
Bassitt, 30, is 10-5 with a 3.95 ERA in 25 games this season, all starts. But he has spent time in the bullpen earlier in his career, including last season when he made four relief appearances.
"You look at my career, most of my career is out of the bullpen, so it's a very easy transition for me," Bassitt said. "I feel really good and I can give them a break if they need it."
Added Melvin: "He's a competitor and he's done both. ... That's one thing about Chris -- he's real versatile. He's pitched out of the bullpen, he's pitched length, he's pitched a couple of innings, so he's added depth for us."