NFL commissioner Roger Goodell said Wednesday there is "significant progress" and "momentum" for pro football to return to the Los Angeles area, but added it is not "inevitable."

His comments come after NFL vice president Eric Grubman said earlier Wednesday that the league could approve a team moving to Los Angeles by the end of the year, with the potential for them to begin playing there in 2016, per the Associated Press. 

Grubman said there has been enough progress "to the point where we think there could be at least one, and maybe two relocation proposals available to act on in time for the 2016 season."

If a team relocates to Los Angeles, it would play in an existing stadium until a new one is built. Grubman said there were several options, but he declined to list them beyond the Rose Bowl and LA Coliseum, which was the Raiders' home before heading back to Oakland in 1995. Anaheim could also be an option. The Rams played in Anaheim before leaving for St. Louis in 1995.

The Rams, Raiders and Chargers are involved in stadium projects in the Los Angeles area that Goodell has called "viable." The NFL also said if a stadium is built by 2018, Los Angeles would be a candidate to host the 2020 Super Bowl.

"I think that when clubs have spent years trying to get something done and have reached that point in time where they explore their alternatives," Grubman said. "Whether it's in Los Angeles or any other market, and that exploration provides something that they can actually go do, then what happens is the timeframe gets defined."

Grubman added the burden is on St. Louis, San Diego and Oakland to present attractive stadium proposals to keep their NFL teams. A new $1 billion stadium has been proposed in St. Louis, but Rams owner Stan Kroenke is planning to build a $1.8 billion facility in Inglewood, Calif.

"There are some really important variables that are beyond our control," Grubman said. "Most important is what the home markets do. That will define what each of the clubs wants to do and what the membership will do."