LOS ANGELES — The Los Angeles Rams will be without their best defensive player for the next month, and possibly longer.Reigning Defensive Player of the Year Myles Garrett is undergoing surgery Monday on the knee he injured early in training camp and is headed to injured reserve. That will keep him out for at least the next four games, and coach Sean McVay isn’t willing to put a timetable on when his star edge rusher will return.“I think it’s all contingent upon how did things go today,” McVay said. “You feel good about it, but I think it’d be unfair to him without having the totality of all the information to put any sort of timeline on it. We know that he’ll be available in four weeks potentially, and we’ll take that a day at a time.”Garrett first started experiencing knee soreness on July 29, which led to a trip to the trainer’s room at Loyola Marymount University and delayed his first training camp news conference by more than an hour. He took two practices off before returning on a maintenance schedule that carried over until shortly after the team returned to its facility in Woodland Hills on Aug. 8.“I’m allowed to get sore,” Garrett, 30, said at the time. “I’m a little old.”San Francisco 49ers expose Los Angeles Rams' 'relative weaknesses'Robert Mays and Derrik KlassenThen, suddenly, he was barely practicing as joint sessions with the Dallas Cowboys and the New Orleans Saints began. McVay said after the Cowboys joint practice that Garrett estimated that he was at around 85 percent of his normal abilities at the time.Garrett finally returned to practice Sept. 6 as the Rams transitioned into regular-season mode with a game on tap against the San Francisco 49ers in Melbourne, Australia. He practiced four out of five days that week, with full sessions on Wednesday and Thursday, and McVay described Garrett’s status as full-go.But then the game arrived, and Garrett played 40 of the team’s 65 defensive snaps in addition to six plays between the punt and field goal block teams. Against the 49ers, Garrett rotated in and out at different times and couldn’t find any rhythm. He finished with zero sacks, zero tackles and zero quarterback hits.The Rams blitzed on just 11.1 percent of plays, per TruMedia. They banked on Garrett and three rushers to get home, but they logged just two quarterback hits and zero sacks on 39 dropbacks from Brock Purdy in the 27-7 loss.“This was the worst version of myself that I’ve put out there,” Garrett said after the game. “I’ve got to be better. I’ve got to find a way to recover and get back to the player I know that I can be and that I’ve shown I’ve been before. … When I was out there, I was a little bit more focused on myself and trying to stay healthy than what they were doing, and it showed. I wasn’t where I needed to be for my team.”Asked about his goals for Week 2 against the New York Giants on “Monday Night Football,” Garrett could only talk about the knee.“Getting healthy,” Garrett said. “That’s the main thing.”That night, McVay and Garrett discussed his knee and decided they needed to explore another avenue. The time off in training camp didn’t give him the freshness they wanted, and the version he showed was a long way from the one who set the NFL’s all-time single-season sacks record with 23 last season for the Cleveland Browns.“I thought we would take an approach where he’d be feeling good enough to go, contribute positive change and be the player that he’s capable of,” McVay said. “That wasn’t the case, and so the next right thing for us is to be able to get this thing fixed.”The Rams opted against having Garrett undergo surgery after the initial injury scare, hoping a maintenance plan could get him to the regular season. If they had done so in early August, Garrett could be more than a month into recovery. That’s the amount of time he must now miss on IR that will keep him out of games against the Giants, Denver Broncos, Philadelphia Eagles and Buffalo Bills in arguably the toughest stretch of the Rams’ schedule. It will be the longest stretch of missed games in his career, as he had only missed five total in the previous nine seasons.The Rams also opted not to have Garrett stay home for the trip to Australia, a decision they did make for Aaron Donald, who is healthy but ramping back into football shape after two years of retirement.“The direction that we went with Myles and the direction we went with Aaron are totally separate situations and circumstances,” McVay said. “With Myles, it was more along the lines of we had been aware of this, thought it was something that he would be able to work through. Obviously being out there and playing in a real game, you learn, hey, maybe that’s not the case, so let’s change course with that, and then Aaron is more just getting him up to speed.”Ultimately, the Rams did not see one week off as making the difference for Garrett’s knee, given that he’s had plenty of time off over the past month. Garrett did spend around 32 hours on the flight, though the team plane featured laydown beds for each player.It creates an unfortunate blow to a defense that needs to rebound from a disappointing performance against the 49ers and a team that needs to dig out of a 0-1 hole. After all, the Rams traded Pro Bowl edge rusher Jared Verse to the Browns in order to acquire Garrett as an upgrade.The Rams could receive a major reinforcement this week if Donald is ready to make his debut for the home opener at SoFi Stadium. McVay wasn’t ready to commit to a timeline for Donald.“He’s going to continue to work his process, and we’ll see what that looks like,” McVay said.Donald decided to return to the Rams, in part, because of Garrett. The blockbuster trade for Garrett came right before Donald embarked on what he called a 14-week journey to train and think like an NFL player again.The potential was alluring, as Garrett and Donald combine for five Defensive Player of the Year awards and can create the first pass rusher tandem in NFL history with 100 career sacks and a 20-sack season for each.The Rams hope that day can come in Week 6 against the Arizona Cardinals, if Garrett can recover from surgery by then.In the meantime, they’ll hope Donald can provide some of the impact and attention Garrett demands from opposing offensive lines, and they’ll look to Pro Bowl edge rusher Byron Young as well as second-year outside linebacker Josaiah Stewart to provide their edge presence. Kobie Turner and Braden Fiske are also options to play the edge on run downs.