Tiger Woods isn't the only person involved in his sex scandal who's underperforming lately -- TMZ has learned mistress #20ish Devon James was pulled from a "celebrity" boxing match last night because she failed a pre-fight physical.
James was scheduled to get in the ring with Susan Finkelstein -- the woman who posted a Craigslist ad offering sex for Philadelphia Phillies tickets ... and Screech was supposed to ref the fight.
But just before the fight -- scheduled to go down in New Jersey -- we're told EMT's determined Devon's blood pressure was too high and expressed concern over her poor performance in the eyeball reaction test.
Eventually, the decision was made to yank her from the fight -- and she was replaced by some other non-famous person. Screech, however, was still allowed to ref the fight.