MINNEAPOLIS — The NFL Players Association filed a lawsuit Thursday to block five of the six player suspensions for violating the league's anti-doping policy.

The suit filed in federal court here is on behalf of Kevin Williams and Pat Williams of the Minnesota Vikings, and Charles Grant, Deuce McAllister and Will Smith of the New Orleans Saints.

The five players were suspended for four games for testing positive in training camp in July and August for the banned diuretic bumetanide, which can be used as a masking agent for steroids. The drug was in a dietary supplement, StarCaps, that did not list the diuretic as an ingredient.

The suit does not include Houston Texans long snapper Bryan Pittman. David Cornwell, Pittman's lawyer, told the AP that his client isn't included because his circumstances "differ substantially from the men who used StarCaps."

In the lawsuit, the NFLPA alleges both the NFL-appointed doctor and the NFL lawyer who administer the league's steroids policy knew the supplement contained the banned drug but never advised the players. It alleges they breached their duty to the players and endangered their physical well-being.

"It's just common sense that someone shouldn't be punished in those circumstances," David Feher, a lawyer for the union, told The Associated Press.

The union has asked for a hearing Friday for a preliminary injunction so the five players can play this weekend. Feher said the hearing hadn't been scheduled as of Thursday morning, and that it wasn't immediately clear which judge would handle it.

"We are taking these steps today in hopes of keeping these players on the playing field," Richard Berthelsen, acting executive director of the NFLPA, said in a statement. "We strongly believe that the doctors and the NFL should have told us and the players what they knew about StarCaps, but for some unknown reason they failed to meet that duty."

An accompanying legal memo says the suspensions could prevent the Vikings and Saints from making the playoffs. It notes that Kevin Williams and Pat Williams have been the centerpieces of the Vikings' defensive line. The Vikings are in first place in the NFC North; the Saints are last in the NFC South and are a longer shot, two games out of the wild card spot with four games to go.

"Not only these players, but their teammates and fans will suffer irreparable harm if the wrongful suspensions are not enjoined," the memo says.

The lawsuit and memo stress the union's view that the NFL had a duty to tell the players and the union that it had known since at least 2006 that StarCaps contained the banned drug, but failed to do so.

Dr. John Lombardo, who oversees the league's steroids policy, "expressly knew and willfully withheld the critical information that StarCaps secretly contained the banned diuretic substance," the filings allege. They also allege that NFL vice president Adolpho Birch, who also oversees the policy, also knew but withheld the information that StarCaps "contained a prohibited substance that could jeopardize the health and career of any player who used the product."