A frightening moment went down in the Nationals' dugout on Monday ... when catcher Keibert Ruiz took a foul ball off the side of the head -- forcing him to exit the game and head to the hospital for a CT scan.
It all unfolded during the Nats' tilt against the San Diego Padres in the top of the fourth inning. Washington designated hitter Josh Bell fouled off a 91 MPH cutter, sending it directly into the Nationals' bench.
Everything seemed fine .