Boyd (knee) will no longer return from the injured list to start against the Giants this weekend after reporting shoulder soreness following his latest rehab start Saturday at Triple-A Iowa, Vinnie Duber of the Chicago Sun-Times reports.
Boyd threw another bullpen session Tuesday and didn't quite feel right afterward, so the Cubs will slow down the 35-year-old's recovery and delay his return from the injured list. It's unknown exactly how far his setback will push back his return, though a clearer picture could emerge once he begins to ramp up his rehab again. Meanwhile, Javier Assad figures to be a top candidate to start in Boyd's place after pitching 6.1 shutout innings out of the bullpen Sunday.