Soccer- USA vs. Argentina - Pablo Mastroeni Red Card?

So Pablo Mastroeni was issued a yellow card early in the second half, which was understandable. But in the 70th minute, he was issued a second yellow card leading to his red card and ejection. What did he do to receive the second yellow card? I've searched the web, watched the replays, and I cant figure it out. It appears Maurice Edu is the player involved with the foul preceding Pablo's second yellow card, so whats the deal?!