Not saying it was an easy play, but if he can get there and get a glove on the ball, that is a catch that should be made. There's no reason to have it simply miss the glove by a few inches, but we have seen that from Seiya on multiple occasions. He should not be a starting right fielder, just like Morel shouldn't be a starting third baseman. Loading a roster with DH's is not a formula for success.