The Los Angeles Rams’ trip to Australia has already proven more costly than simply losing a game. Reigning Defensive Player of the Year Myles Garrett will undergo knee surgery and is heading to injured reserve, a team source confirmed to The Athletic.Garrett suffered the knee injury early in training camp and managed it for several weeks, mostly with rest and rehab. He practiced a couple of times after camp returned to the Rams’ practice facility, then returned for practices ahead of the Week 1 trip to Melbourne, Australia.But Garrett wasn’t nearly himself in the 27-7 loss to the San Francisco 49ers in Melbourne. He subbed in and out of the game and finished without a sack, tackle or quarterback hit, and then said after the game that he wasn’t healthy. “This was the worst version of myself,” he said.San Francisco 49ers expose Los Angeles Rams' 'relative weaknesses'Robert Mays and Derrik KlassenNow, Garrett will miss at least the next four games on injured reserve. He is eligible to return Oct. 18 against the Arizona Cardinals if he can rehab the knee in that time.It’s a significant blow given what the Rams traded to acquire Garrett from the Cleveland Browns. Los Angeles sent Pro Bowl edge rusher Jared Verse, a 2027 first-round pick, a 2028 second-round pick and a 2029 third-rounder to Cleveland for the two-time Defensive Player of the Year.Landing Garrett was also key in convincing three-time Defensive Player of the Year Aaron Donald to return from retirement and join this year’s squad, though Donald did not travel to Melbourne to complete his ramp-up after two seasons away.Now, Donald and Garrett won’t be able to line up next to each other until at least Week 6.It’s unclear why the Rams chose to travel with Garrett and have him play against the 49ers while resting Donald. Coach Sean McVay consistently said Garrett’s absences from practice were merely precautionary and said after the Week 1 loss that he believed Garrett was healthy.Without Garrett, Byron Young and Josaiah Stewart will man the edge roles, with Kobie Turner and Braden Fiske playing more as edge options on run downs.The Rams will look to improve elsewhere after a rough showing against the 49ers, in which they managed zero sacks and just two quarterback hits. They have another blockbuster acquisition on defense to help with that: two-time All-Pro cornerback Trent McDuffie, one of the lone standouts in the loss to the 49ers.The Rams will next host the New York Giants on “Monday Night Football” in Week 2.