Per the ESPN Dallas blog, Ron Washington said after the game that he pulled Darren O'Day in the 8th, and went with Neftali Feliz to face Jason Bartlett, because Bartlett was 3 for 5 against O'Day in his career.
Washington confirmed that Feliz would have faced Jason Jaso, who was after Bartlett, regardless, and thus he opted to go to Feliz to face Bartlett as well.
The move was weird, but I don't think the decision was that big of a deal -- yes, it meant pulling a pitcher when you were already running low on relievers, but it simply meant that Feliz would have faced one more batter than he would have otherwise.
In any case, Feliz was off and ended up getting rocked, but I don't have a problem with Feliz coming in in the 8th inning in a key situation.
I do think, though, that pulling O'Day because Bartlett was 3 for 5 against him lifetime means that Wash was using a very questionable rationale for making the move.