Wheeler (shoulder) skipped his scheduled Thursday bullpen session due to the flu, Jim Salisbury of NBC Sports Philadelphia reports.
Wheeler has already been ruled out for an Opening Day start, as his throwing program was delayed over the winter by shoulder soreness. There haven't yet been reports that he's dealing with any significant shoulder issue, so he wasn't expected to miss much more than one start, but another slight delay from the flu could push him back further. A brief trip to the injured list could be in play if his buildup process keeps getting delayed.