Right, and what's the worse case scenario here? Marco Hernandez makes an out. And you play on.Really? If Shaw gets a hit in the 9th to tie the game, then Papi is on deck, and could either be hitting in the 9th (if Mookie walks to load the bases) or leading off the bottom of the 10th. So the possibility was not at all remote that Papi could have had another meaningful AB.
In this case, I think JF did the right thing by using the PR when he did.
Give yourself the best chance to tie the game, then worry about how to get it done in extra innings.