Patrick Power, 26, was arrested Thursday on suspicion of felony assault.
He was taken into custody during a search of his home for evidence related to the June 25 incident, in which Gaelic football player Mark McGovern, an Irish player visiting the U.S., was seriously injured during a game on Treasure Island.
Prosecutors have discharged the case against Power pending further investigation, district attorney's spokesman Seth Steward said.
Power was released from county jail on Friday evening, sheriff's spokeswoman Eileen Hirst said.
Gaelic football is a mix between soccer and rugby in which players kick or throw a ball through goalposts to score points.
According to www.support4markmcgovern.com, a website maintained by McGovern's family and supporters, McGovern was injured in a hit that occurred away from the ball during the game.
McGovern, who came to the Bay Area to play for the San Francisco Gaelic Athletic Association over the summer, suffered a severe brain injury and was in critical condition after also contracting pneumonia and infection from the MRSA bug, according to the website.
His condition has since improved and he is undergoing rehabilitation, but his family is seeking help with medical bills, which have already totaled more than $1 million, according to the website.
Donations can be made on the www.support4markmcgovern.com website, or by mail to Mark McGovern Fund at 117 Dalewood Way, San Francisco, 94127.