The National Football League announced Thursday it would welcome its players back to work and gradually resume league business beginning Friday morning, even as its attorneys spent the day trying to convince an appellate court in St. Louis to shut down the league’s operations once again.

League officials promised players access to team facilities, coaches and staff beginning Friday at 8 a.m. but refused to guarantee the opening of more complex business such as player transactions and signings. And they aggressively sought a temporary stay from the 8th Circuit Court of Appeals in St. Louis by early Friday that would short-circuit the whole plan.

 “We’re opening our doors at 8 o’clock tomorrow morning,” NFL Commissioner Roger Goodell said at Radio City Music Hall in New York, about 21 / 2 hours before the first round of the NFL draft Thursday night. “The players will be back in. . . . We’ll wait, and if the appeals court tells us something different, then we’ll have to respond to that.”

Goodell declined to discuss how the league would handle free agent signings or player trades, saying details would be revealed when they are ready. Experts say the league is wary of opening up the free agent market because it has no operating rules, but player representatives say the league has had a plan for months and is stalling.

James Quinn, an attorney for the players, said Tuesday that if free agency did not begin by Wednesday, he would have concerns about improper collusion by teams.

“We’re putting together the player transaction rules so we can do it in an orderly way,” Goodell said.

On Wednesday night, U.S. District Judge Susan Richard Nelson provided her second decisive ruling of the week in favor of the players by refusing to grant a stay of her decision Monday to lift the lockout imposed by owners March 12. The league appealed the decision two hours later.

NFL attorneys argued Thursday in motions and letters to the appeals court that the league would suffer irreparable harm if forced to resume operations without a collective bargaining agreement.

Players’ representatives urged players to report for work Thursday morning as they did Tuesday after Nelson’s initial ruling, saying the league would be in contempt of court if it denied them entry and refused to do business.

Quinn and Jeffrey Kessler, another player attorney, wrote in a memo to players and agents that Nelson’s decision to reject the NFL’s request for a stay meant “the order ending the lockout is in full, immediate force.”

Yet Tennessee Titans players complained they were greeted by armed security guards and locked gates. Linebacker Lorenzo Alexander and center Casey Rabach were turned away at Redskins Park. Detroit Lions players were told to come back Monday, and that organized team activities would start Wednesday, according to published reports.

The league told teams to courteously turn away players, maintaining that it could not conduct business without an organized plan. NFL attorneys complained in court filings Thursday that doing any business at all could put the league in danger of further anti-trust claims from the players, who sued owners and the NFL for such violations on March 11, when contract talks broke down and they dissolved their labor union.

For Thursday night’s draft, allowed by a provision in the expired collective bargaining agreement between the league and the players’ union, trades could involve picks but not players.

On Friday morning, the league said, offseason workout programs for players could begin and players could work out at team facilities at other times without supervision by club officials, as long as they provided proof of medical insurance. The league also said it would “promptly” make arrangements to resume the counseling, rehabilitation and treatment portions of its drug-testing programs.

Once they open their doors Friday, league owners will have to be extremely careful about demonstrating any appearance of collusion, according to New York University law professor Robert Boland.

Apprehension about the consequences of their business dealings, Boland said, might mean teams treat this unusual open-for-business stretch with little agreement and in widely varying ways.

“Teams are not going to be able to share as much information and the league is not going to be able to dictate as much to individual teams,” said Boland, an expert in labor and anti-trust law. “You will have great, great disparity as to what teams will do. Some will sign priority free agents; some will sign depth guys; others will sign no one. I think teams will run the gamut on that.”

Boland said he thought some teams would hesitate for fear they would run into problems with an eventual salary cap or other rules instituted later that could compromise deals made under an uncertain system.

Free agency “could offer opportunity, but it could also offer punishment,” he said. “Nobody knows quite what to do.”

Even as the league advertised that it would be opening its doors Friday, it tried mightily to convince the appellate court to grant a stay that would reinstate the lockout. It sought both a stay pending the appeal of Nelson’s decision to lift the lockout — which it speculated could be heard by June — as well as a temporary stay as the court considered the matter.

In a letter to the appellate court, NFL attorney Paul D. Clement said the players had threatened “immediate contempt sanctions” if they did not immediately comply with the district court’s order to lift the lockout. The letter claimed “the plaintiffs’ threat of contempt only underscores the need for a temporary stay.”

In a letter to the court later Thursday, players’ attorney Theodore B. Olson said the NFL claims showed “lack of merit.
 “Contrary to the assertion in their letter, the NFL defendants have carefully prepared for this result and are more than ready to resume operations,” Olson wrote.