Washington Spirit midfielder Croix Bethune will not play again this season ... and it's all because she hurled out a ceremonial first pitch at a Nationals game last week.
The 23-year-old was tapped by the MLB org. to kick off its tilt with the Yankees on Aug. 28 following her gold medal success at the Paris Games ... and, initially, everything appeared to go off without a hitch.
The soccer star -- who was at the D.C. game with several other Olympians -- toed the rubber, threw the ball to a catcher .