Cobb was scheduled to pitch in an intrasquad game Sunday.
"Probably won't know anything until (Monday) when Cobb comes in and see how he feels," Tampa Bay manager Kevin Cash said before the Rays played the New York Yankees. "To my knowledge he could have pitched today."
Cobb returned from Tommy John surgery late last season and is trying to regain the pre-injury form that had him on track to be the opening-day starter in 2015.
Shortstop Tim Beckham didn't play in the Yankees' game because of hip flexor tightness.