First you need to get to extra innings and you only have 6 outs left. Giving one up because you may tie in the five left is stupid. And this isn't just this year, Jenkin's hasn't hit LH pitching ever.
Yes Kinney should be able to get Valentin out. Hell, Matt Erickson should get Valentin out. But Yost should realize that Kinney has problems with men on base. He needs to work on that, but not in a 5-2 game but in a 10-2 game.