The right-hander, who is rehabbing a right rotator cuff strain in Mesa, Ariz., told Cubs coaches that he felt a twinge in his right shoulder.
Cashner is going home to Texas on Tuesday for personal reasons unrelated to his injury, but before he leaves, he'll be evaluated by the team's medical staff. Although the Chicago Tribune and MLB.com reported that Cashner will get another MRI, a source told ESPNChicago.com that getting the procedure may depend on the results of an examination.
Cashner and fellow right-hander Randy Wells (right forearm strain) have both been on the disabled list since April 8. Monday's setback was Cashner's first since he began throwing the ball again in the third week of April.
Cashner and Wells left the team on May 5 after the Los Angeles trip to begin working at the Cubs' minor league complex.
Wells will make his first rehab start on Tuesday night in Peoria for the Single-A Chiefs and if everything goes all right, his second start will be for Triple-A Iowa five days later.
Bruce Levine covers the Cubs for ESPNChicago.com and ESPN 1000.