Both the National Football League and the NFL Players Association will hold meetings this week that could affect the eventual outcome of the current contract talks between the two sides.

The NFLPA is meeting here starting Monday. The three-day session is expected to attract more than 500 players, making it one of the largest conventions of professional athletes in history. They will be lured by concern over the contract that expires this summer and the union's demand for a share of the league's gross revenue, an issue that could lead to a strike.

The league's annual meeting will begin Sunday in Phoenix and will last until Friday. A highlight should be a midweek report by the Management Council, the NFL's labor negotiating arm. The council already has rejected formally the union's demand for a percentage of the gross.

League committees also will discuss hot- and cold-weather playoff guidelines, pass-interference penalties, two-point conversions and the use of kicking tees on extra points and field goals.

Commissioner Pete Rozelle will give an update on the current trial in Los Angeles involving Al Davis' attempt to move the Oakland Raiders, and on the league's negotiations on a new network-TV contract.

While league executives are hearing these reports, they also will be watching the players' meeting.

"They will want to see if we really have unity," Gene Upshaw, the NFLPA president, said. "They will be looking for signs of weakness. They won't find any. What they will find is togetherness.

"For us, the most important aspect of the convention will be informational. We want to make sure the players understand everthing about the contract demands."

NFLPA executives emphasize that the convention will not be voting on the basic contract issues. Those already have been decided by team player representatives and have been forwarded to the league.

But there is certain to be much discussion concerning percentage of the gross. Prior to the start of negotiations, the NFLPA was considering asking for 55 percent of the gross. But at the moment, the union is not asking for a specific figure. Upshaw says that figure will be determined later, probably through negotiations and discussions here.

There has been some disagreement within the membership, but no formal countermovement has been organized, and its emergence here seems unlikely.