I'd say the majority of great line drive catches by pitchers are self-preservation. They throw their glove up to protect themselves and just so happen to catch the ball. It's scary for a split second, but once the catch is made, it becomes a great play.
There are also the lucky line drive catches, when the pitcher just flings his glove in a general direction and the ball finds him. Those are the "the ball caught him, he didn't catch the ball" catches. Tuesday night, Rangers righty Nick Martinez made one of those catches against Angels shortstop Andrelton Simmons, and this one was an insane behind the back grab. Check it out:
And he turned it into a double play too! Incredible. You might see a pitcher reach down and snag a soft ground ball behind his legs once in a while, but a line drive like that? That never happens. Martinez just threw his glove up and the ball found it. Amazing.
How did Angels manager Mike Scioscia feel about the catch? His face says it all:
Yeah, it's been that kind of season for the Angels.
