[Travis]

Well, the thing is, because he chased him down, Pierre doesn't technically have to return straight to the base, hence the pseudo run down situation. It's not a true run down because eventually he'll just run him out of room, but it does prolong the play which allowed Ethier to cross home before the out was recorded. In that sense the play was actually called correctly. As bad as it is for the umps to have missed the call on the tag up it was still a very poor choice on the part of Lopez given that he introduces all sorts of (unlikely) variables into the play (he could drop the ball while chasing/tagging Pierre, etc).