Floyd, who was scratched from Monday's start against the Boston Red Sox, had an MRI in Chicago on Sunday, and it revealed no structural damage. His DL stay is retroactive to July 8.
With Floyd going to the DL, the White Sox activated Philip Humber in time for his start against the Red Sox on Tuesday. Humber, who has been out since June 22 with a right elbow flexor strain, was on a rehab assignment at Double-A Birmingham.
Humber has struggled since throwing a perfect game on April 21. He had an 8.22 ERA in three June starts before landing on the DL. He is 3-4 with a 6.01 ERA in 12 starts this season.
Floyd is 7-8 with a 4.54 ERA in 17 starts this season. He has allowed 101 hits, 52 earned runs and 31 walks and has struck out 91 batters in 103 innings. He's allowed four runs in his last four starts.
This is the first DL stint in Floyd's 11-year career.