DENVER — A former Arena Football League player has sued a Denver doctor and clinic, saying he suffered permanent brain damage because he didn't get standard care after a concussion during the 2008 season.

Clay Rush, a kicker for the now-defunct Colorado Crush, filed suit Wednesday in Denver District Court against Dr. Saurabh Mangalik and HealthOne Clinic Services.

The lawsuit says Rush's health problems started in April 2008 when he suffered hits to the head in two games two weeks apart. He showed symptoms of a concussion, including headaches, nausea, dizziness, blurred vision and insomnia, but wasn't properly evaluated or monitored, the lawsuit says.

The lawsuit, first reported by The New York Times, says Mangalik was designated the team physician and it claims Mangalik didn't follow standard practice for assessing and treating a head injury.

A recording on Mangalik's phone said he was out of the office Friday, and he didn't immediately return a message left by The Associated Press. He told the Times he followed the standard protocol for a head injury in Rush's case.

Linda Kanamine of Healthone Clinic Services said the company's lawyers were still reviewing the lawsuit and that the company had no comment.

When Rush rested for a week after the second hit, some of his symptoms cleared up, and Mangalik cleared him to play, the lawsuit says. When Rush played again on about April 25, the symptoms worsened, the suit says.

"As soon as he exerted himself, he ended up creating more problems," Steven Shapiro, one of Rush's attorneys, said Friday. "That created a permanent brain injury."

"If he would have not played (in the April 25 game) and rested and been kept off and observed, he probably would have been fine," Shapiro said.

Mangalik told the Times he repeatedly told Rush and team trainers that Rush shouldn't practice or play until his symptoms cleared.

"I'm not sure why he felt he was allowed to go back," Mangalik told the Times. "I don't know if he told the team he had symptoms and they let him play anyway, or if he didn't have symptoms and now is saying that he did. I don't know that. All I know is what he told me and I told him."

The lawsuit seeks unspecified damages.

Rush, who lives in the town of Superior about 15 miles northwest of Denver, has not been able to work, Shapiro said. He gets psychological treatment, undergoes rehabilitation for pain, dizziness and balance problems and gets occupational and speech therapy.

Brain-injury lawsuits by professional athletes are rare because in most cases they are covered by workers' compensation laws and cannot sue, said Michael Kaplen, a Pleasantville, N.Y., attorney who specializes in brain injury cases.

The Crush, which was Rush's employer at the time, stopped playing when the Arena Football League folded in August 2009.