Bassitt was recalled from Triple-A Las Vegas on Wednesday.
Bassitt will join the big club in place of Marco Estrada, who was sent to the injured list with a lumbar strain. According to John Shea of the San Francisco Chronicle, Bassit will tentatively slot into Estrada's place in the rotation, though that could change if he's needed out of the bullpen. He's made three minor-league appearances this season while working back from a lower-leg injury, posting a 3.27 ERA, 0.91 WHIP and 16:2 K:BB in 11 innings during those outings. Bassitt worked as both a starter and reliever for the A's last season, notching a 3.02 ERA, 1.24 WHIP and 7.7 K/9 in 47.2 innings.