Strasburg was hurt during a workout Thursday, and an MRI exam showed inflammation. He is scheduled to travel to Washington on Friday to be examined by the Nationals' team doctor.
The Nationals issued a news release saying Strasburg's injury "is not considered serious."
The title game is Saturday.
Strasburg also was held out of a scheduled start in the Arizona Fall League Rising Stars game Nov. 7 because of a strained neck muscle.
The San Diego State right-hander signed a record $15.1 million contract after being the top pick in June's amateur draft.