Prosecutors say two groups sparred several times before the July 2009 melee that left 22-year-old David Sale Jr. of Lansdale dead.
Three Philadelphia men are facing murder charges over the attack in a parking lot near Citizens Bank Park.
Thirty-year-old Francis Kirchner is charged with first-degree murder for allegedly delivering the fatal blow.
Thirty-seven-year-old Charles Bowers and 48-year-old Jim Groves are charged with third-degree murder.
The defendants had gone to the game on a trip sponsored by a city tavern. The feud between the groups allegedly started over a spilled beer.
Defense lawyers have argued that it will be hard to prove who did what during the fight.
In court on Wednesday, there were back-room negotiations over possible guilty pleas. However, talks fell through.
In opening arguments to the jury, prosecutor Fichard Sax said Sale was on the ground defenseless when Kirchner "teed him up like a football and punted his head, causing massive hemorrhage of the brain."
Kirchner's lawyer, Jack McMahon, said Sale did not deserve to die, but he was a "drunken, arrogant, obnoxious, rude, fighting person that night, caught up in a classic melee."
Kirchner faces life in prison. Bowers and Grove could get 20 to 40 years if convicted.