Ralston joined the Revolution in 2002 after the Tampa Bay Mutiny were contracted by Major League Soccer. And he rejoined the Revolution yesterday, as AC St. Louis’s future in the US Soccer Federation Division 2 league has been jeopardized by a loss of investors.

“It happened pretty quickly, to be honest,’’ Ralston said. “Nobody knows what’s going on. Our paychecks were a little late at one point. My agent spoke to the Revolution, but I wasn’t even thinking about it. I was staying focused there, concentrating on the group of guys there.

“I talked with ownership there and they said, ‘We don’t know what’s going to happen.’ They could end up folding next week or they could make it to the end of the season, nobody knows.’’

Ralston underwent knee surgery after being injured playing for the Revolution in a game at Gillette Stadium last September. Doubts about his ability to recover led the Revolution to initially offer him a contract that would have cut his $150,000 salary. He then received a similar offer to be a player/assistant coach with AC St. Louis, a new team in the USSF.

Ralston, 35, did not publicly criticize the Revolution over the negotiations when he took the St. Louis offer and relocated his family.

“We took everything back, that’s the hardest part,’’ Ralston said. “With three kids, figuring out the school stuff, moving and packing — the rest is easy because I still know so many people here.

“When I got back here, to the stadium and locker room, I felt [comfortable]. There are some new faces but not a lot’s changed. I feel like this was an extended vacation and this is a great opportunity to finish my career with the Revolution.’’

Ralston returned to action two weeks ago, playing 35 minutes against Tampa Bay, then going 90 minutes against Minnesota.

“In the first half I felt sharp, but in the second half I felt it in my legs,’’ Ralston said. “I need to get my match fitness back and try to get sharp. But after the [Minnesota] game I felt fine.’’

With Ralston, the Revolution could return to the 3-5-2 formation that has been a key to their success. The midfielder has played in 412 MLS games (including playoffs) and last season scored 7 goals in 20 matches.

“Unfortunately, I haven’t seen any games because they weren’t shown in St. Louis,’’ Ralston said. “I’ve been following the team and talking to guys.

“Looking at the team, they have quality, some great players, but for whatever reason it hasn’t clicked yet. When we get everyone healthy, we have enough talent to compete with anybody.’’

Ralston’s departure reduces the AC St. Louis payroll significantly. Coach Claude Anelka, brother of Chelsea’s Nicolas Anelka, is earning about $200,000, more than many MLS coaches.

“I think the commitment was there but the other ownership group, the European investors, walked,’’ Ralston said. “They said they weren’t going to do it anymore.

“We had played three home games, and it’s a small venue, but we had great crowds, 5,000-6,000, and it had a European feel, with smoke bombs and flares.

“I feel fortunate I had another option. There’s some guys there who won’t have that, so I hope they make it at least to the end of the season. We were hoping to build something there.’’

St. Louis has been one of the country’s hotbeds of soccer, and in recent seasons, nearly half the Revolution starting lineup had been from the city. Tampa, meanwhile, was among the most successful franchises in the North American Soccer League but failed to attract significant local ownership in six MLS seasons.

Frank Dell’Apa can be reached at f_dellapa@globe.com.