They both blew it but Wire screwed up more. Posey was supposed to jam Gaines at the LOS and slow him up, releasing him to Wire. However with the mis-direction, it threw Posey off a bit and he didn't get the jam. Then Wire takes a misstep to his left when he should have been going right to shade the TE, lost him, and boom, TD. Go figure, Milloy probably makes that play, but gets hurt just a few plays before.
BTW, it looked like an Achilles when I first saw it, but didn't notice any foot drop when he walked to the sidelines. I haven't heard any reports so I'm assuming no news is good news.