Terrifying moment for Christian Vazquez during the Twins game Wednesday ... he was struck in the helmet by a foul ball while he was standing in the on-deck circle -- but somehow, he ended up being OK.
The crazy scene happened just minutes ago while Donovan Solano was up to bat against Tigers pitcher Reese Olson.
The Minnesota first baseman took a big hack on a slider, but he just missed barreling it up -- and the ball went foul ... making a beeline right for Vazquez's head.