Nelson Rivas Headbutts Antoine Hoppenot During Montreal Impact-Philadelphia Union Match (VIDEO)

Montreal's 2-0 win over the Philadelphia Union on Saturday night was marred by a nasty altercation in the middle of the second half that resulted in two red cards.

In the 67th minute, Union midfielder Antoine Hoppenot got tangled up with Impact defender Nelson and shoved him to the ground. Rivas retaliated right away, walking right up to Hoppenot and delivering a vicious headbutt. A scuffle ensued and after the teams were separated, Rivas was handed a red card. Philadelphia forward Jack McInerney was also given a red card for intervening and pushing Rivas.

Union manager John Hackworth told reporters after the loss that he didn't think his team should have been down a man for the the rest of the match.

"We should be up a man. It's unbelievable that we're not up a man for the last 22-plus minutes of that match," Hackworth said, via "You cannot tell me that a headbutt to the nose and cheekbone, and a player literally going to push another player, is even justifiable for equal punishment. There's no possibility."

Rivas is expected to be suspended for at least Montreal's next match against the New England Revolution and maybe more.