Bassitt will pitch for Nashville on July 19 and be available to start for the A's on July 25 against the Giants, the first day they need a fifth starter again. It's unlikely that righty Jesse Hahn, shut down with a forearm strain, will be ready to pitch by then.
For Otero, this is his second stint with the A's this year, having struggled to the tune of a 6.29 ERA in 23 appearances ahead of his June 5 demotion. He went on to post a 1.08 ERA in nine games for the Sounds and didn't allow a run in his final 11 innings.
Last year, he went 8-2 with a 2.28 ERA in 72 games out of Oakland's bullpen.
"I tried not to do anything too crazy, just go down there and pitch," Otero said. "I was really focusing on just trying to improve my fastball command like I know I can. Other than that, just trying to refine my secondary pitches and working hard down there."
Triple-A opponents were hitting .242 off Otero, who scattered 15 hits over 16 2/3 innings, but allowed only two runs and struck out 13, walking two.
"His last several times out were good," A's manager Bob Melvin said. "Went multiple innings and was doing the things that we're used to seeing him do. Everybody goes through a tough time from time to time, but he's shown that he can be one of the most versatile guys that we have in our bullpen, and when he's pitching well, he's a nice resource to have."
Jane Lee is a reporter for MLB.com. Read her blog, Major Lee-ague, follow her on Twitter @JaneMLB and listen to her podcast. This story was not subject to the approval of Major League Baseball or its clubs.