Minnesota United captain Michael Boxall and Real Salt Lake defender Brayan Vera entangled on a corner kick and slammed into the grass late in Wednesday’s match at America First Field. Vera stayed down, holding his head after taking the brunt of the impact. That was the opening salvo. In an apparent retaliation a few minutes later, Vera spit at Boxall, who then confronted Vera and was issued a yellow card. Upon video review, referee Ricardo Monte…