Magruder also reports that Brandon McCarthy will be out until the end of July, saying that Cahill "may be longer." The team currently has just four starters, with prospect Tyler Skaggs being a potential replacement in the rotation for the right-hander.
Cahill is trying to recover from a hip contusion, which landed him on the disabled list on July 1.
Cahill, 25, has an ERA of 4.66 in 96 2/3 innings this year for the Diamondbacks. He has pitched at least 200 innings for them each of the last two seasons, and most of his value comes from his ability to eat innings at a decent rate of effectiveness.
Arizona has a good amount of pitching depth, and could also go to long-reliever Josh Collmenter if they do not want to promote a prospect from the minor leagues.