So what sparked that angry exchange between coaches Preki and Dominic Kinnear Saturday in the melee that broke out seconds after Chivas USA and Houston had played a 0-0 tie at Home Depot Center?
According to a source who spoke with one of the participants - not Preki or Kinnear - tensions between the benches had been boiling since referee Baldomero Toledo sent off Chivas USA's Lawson Vaughn late in the first half for a studs-up, scissor tackle on Richard Mulrooney.
The Chivas USA coaches and players got hotter in the second half when Houston defender Pat Ianni felledMaykel Galindo with a harsh tackle and wasn't ejected, and they were incensed when Jonathan Bornstein went down under a Brian Mullan tackle in the penalty area and Toledo let play continue.
After Ianni's foul, for which he was cautioned, Galindo hobbled off and was replaced by Jason Hernandez.
Players and coaches on both benches harangued the officials, and Chivas USA goalkeeping coach Zak Abdelbadgered Toledo and fourth official Ramon Hernandez for the rest of the match, insisting Ianni should have been sent off.
After the final whistle, Preki went to shake hands with Kinnear. As he took Preki's hand, Kinnear said something to Abdel, who was behind Preki.
According to the source, Kinnear said, "F*** off, Zak," which prompted Preki to angrily challenge Kinnear's choice of language while addressing one of his assistants.
Tensions escalated and Abdel and a few others tried to play peacemaker as players from both teams joined the skirmish.
Toledo did not discipline any players or coaches after the fact but he reportedly noted the incident in his official game report that will be reviewed by senior director of game operations Joe Machnik.
Preki lamented the red card in the postgame press conference, saying it should have been a caution and perhaps a stern word from the referee, but not a red card.
Preki could be fined for publicly criticizing an official's decisions.
Revs coach Steve Nicol took a $2,000 hit last year when he objected to a suspension meted out to Shalrie Joseph for a incident missed by the referee, and Wizards coach Curt Onalfo was dinged $1,000 in July.
The Mullan-Bornstein incident didn't seem worthy of a whistle, but both the Vaughn and Ianni tackles were judgment calls. Vaughn might have been caught in multiple jeopardy: his tackle was late, the studs were visible, his second leg caught Mulrooney's foot, and the tackle came from behind.
Click HERE for highlights of the Chivas USA-Houston game.