For the second straight day, the A's pitching staff took a big hit.
On Friday, ace Frankie Montas was suspended for 80 games. A day later, the A's lost All-Star closer Blake Treinen to the injured list.
"Blake has a mild shoulder issue right now," manager Bob Melvin told the media after the A's 4-2 win over the Rays at the Coliseum. "It's muscular in nature and we're going to put him on the IL."
Coming off a historic 2018 season, Treinen hasn't been as dominant this season. In 35 1/3 inning, he's posted a 4.08 ERA and has converted 16 of 18 save opportunities.
In Treinen's last outing on Thursday against Tampa Bay, he gave up two hits, three earned runs, walked two and failed to record an out.
[RELATED: Possible options to replace Montas]
With Treinen out for at least 10 days, Melvin said that Liam Hendriks will take over as the A's closer.
Losing Treinen is another big blow for an A's team that is trying to stay close in the AL Wild Card race. After Saturday's win, Oakland is 1.5 games behind the Boston Red Sox for the second Wild Card spot.