The only reason he put Price in was because Loup and Cecil- the only two left handed bullpen pitchers- weren't available.
In Game 4, you either go with one of your right handers, who all range from barely decent to terrible against lefties, save Tepera (and do you really want Tepera pitching in an elimination game?) in your bullpen and hope they can not blow a 6 run lead in 5 innings against a lineup chock full of lefty power hitters behind lefty guys who get on base, in a hitters park no less, or you go with Price to clinch the game.
It was a risk, thankfully Stroman pitched well enough- as good as Cole Hamels- and Sanchez/Osuna only had to go through the top of the order left handers a single time. But makes far greater sense when you consider that Loup and Cecil weren't available. And I'm not saying I agree completely with Gibbons, but in this case, we don't have to completely exonerate him: just come up with rationale that makes sense. The above certainly seems reasonable to me.
Wish Cecil weren't injured on a complete fluke injury, he was their best reliever regardless of handedness. ****ing dynamite.