Red Sox's Tyler O'Neill Leaves Game Bloodied After Scary Collision With Teammate

Tyler O'Neill was forced to leave Boston's Patriots' Day game early on Monday ... after he suffered a bloody head wound in a collision with his teammate.

The scary moment happened in the seventh inning of the Red Sox's tilt with the Guardians at Fenway Park ... when Estevan Florial hit a popup to shallow left field that O'Neill and third baseman Rafael Devers both tried to catch.

You can see in footage from the game's broadcast, as they were looking toward the sky to haul in the ball, they didn't see each other -- and they ended up running into one another.

Replays showed the guys' heads collided first ... sending both dudes flying to the turf in a world of pain.

O'Neill seemed to suffer the worst of it -- as he looked to be bleeding from a few parts of his forehead. Devers, though, stayed on the ground for a while too ... and appeared woozy when he got up.

Trainers raced out to tend to both players, and, eventually, they each made their way to the dugout under their own power.

O'Neill was not able to return to the contest ... though Devers did remain in the lineup.