Greater Western Sydney key forward Jon Patton was concussed outside a Los Angeles bar in what the AFL club said was an unprovoked assault.
Patton was taken to hospital on Wednesday night (AEST), but he was cleared of serious injury and released.
The 22-year-old was with teammate Tomas Bugg when he was struck on the side of the head.
"Witnesses interviewed by Los Angeles police have stated that Patton was the innocent victim of an unprovoked assault," the Giants said on their website.
"LA Police have confirmed that a local male was arrested following the incident."
One of the nightmare scenarios for AFL clubs is their players being hurt or finding themselves in trouble while they are on end-of-season trips.
Three years ago, Port Adelaide's John McCarthy died when he fell from a rooftop in Las Vegas at the start of a post-season holiday with teammates.
Patton has endured a dreadful run with injury in his AFL career.
The 2011 No.1 draft pick resumed senior football in round 19 this season after a knee reconstruction.
Patton made his AFL debut in round 12, 2012, managing only 32 games because of his injuries.