The Cubs placed Steele (back) on the 15-day injured list Monday.
The transaction is retroactive to Friday, making Sept. 17 the earliest date Steele will be eligible to rejoin the Cubs. Steele hadn't pitched since Aug. 26, as he missed his subsequent turn through the rotation while he was on the restricted list due to him being ineligible to cross the Canadian border for the Cubs' series in Toronto. He had been expected to rejoin the rotation for the Cubs' first game of the week Tuesday against the Reds, but he was still experiencing back soreness stemming from the Aug. 26 start. The Cubs will now give the prized lefty some extra time to heal up, while prospect Hayden Wesneski was called up from Triple-A Iowa to presumably fill Steele's spot in Chicago's six-man rotation.