Left-hander Jason Waddell was called up to replace Cotts.
Infielder Bobby Scales, who had been unavailable due to severe flu symptoms the past two days, also was optioned to Iowa.
Shortstop Andres Blanco was brought up from Triple-A to replace Scales.
With Miles unavailable for at least two weeks, Blanco will play some shortstop to give every-day shortstop Ryan Theriot some time off. Blanco was hitting .314 at Iowa.
Fox has been the hitting sensation of the minor leagues this year, batting .423 with 17 home runs and 50 RBIs through Tuesday night.
Manager Lou Piniella most likely will use him in the outfield and occasionally at third or first base, although defense has been a question mark for Fox, who's a converted catcher.