The Marlins will be on the hunt for a new third base coach for the next few weeks ... 'cause their current one, Jody Reed, suffered a broken leg after he was struck by a foul ball on Wednesday.
The painful moment all went down during Miami's game against the St. Louis Cardinals at Busch Stadium ... when Jesus Sanchez was in the batter's box taking hacks against Dakota Hudson.
At one point during the AB, Sanchez lined a pitch right at Reed ... and it hit the coach flush in the lower leg.
"Look out Jody Reed!" the game's announcer said after the baseball tagged him.
Reed tried to walk it off ... but he had to exit the contest due to the pain. Later in the evening, Marlins manager Skip Schumaker revealed tests showed Reed had fractured a bone.
"He's going to be down," the coach said. "I'm not sure how long, but he had X-rays and the doctor said it was broke, so we'll see how long he's out for, unfortunately."
Reed -- a former MLB second baseman -- joined the Marlins' staff this year. He was replaced during Wednesday's game by Griffin Benedict, though it's unclear who Schumaker will have fill in going forward while Reed recovers.