Oakland optioned Basso to the Arizona Complex League Athletics on Friday.
The move makes room on the A's 28-man roster for the reinstatement of right-hander Ross Stripling (back) from the 15-day injured list. Basso has made four starts for the Athletics in September, going 1-1 with a 3.79 ERA, 1.32 WHIP and 16:5 K:BB over 19 innings.