The South African secured his place in the annals of the golfing greats with his victory at the 2010 Open Championship but since then he has endured a string of near misses in golf's biggest four events, losing two play-offs and finishing second twice in as many months this year.
On Sunday at Torrey Pines Golf Course, he held a one shot lead on the back nine but Jon Rahm birdied the 17th and 18th in spectacular style to leapfrog the 38-year-old and leave him needing some magic of his own.
Oosthuizen found a hazard off the tee at the 17th for a bogey and was forced to lay up on the par five last where he needed an eagle, eventually carding a birdie to finish a single shot behind Rahm.
"I'm second again," he said. "No, look, it's frustrating. It's disappointing. I'm playing good golf but winning a Major Championship is not just going to happen. You need to go out and play good golf. I played good today but I didn't play good enough.
I’ll keep knocking on that major door. Gave it my best and am thankful to the @USGA and @usopengolf for a great week. Enjoy the win, @JonRahmpga! Nothing like a major win on Father’s Day as a new dad. #USOpen pic.twitter.com/WlXjzDhX6R— Louis Oosthuizen (@Louis57TM) June 21, 2021
"I definitely left a few putts or shots out there.
"I took the tee shot on at 17 and I knew it was a crucial hole for me to take it on and give myself a birdie opportunity. I didn't pull it off but standing on that tee again, I'll probably do the same thing, taking a driver and taking the shot on.
"I feel like I had my shots, I went for it, and that's what you have to do to win Majors. Sometimes it goes your way and other times it doesn't.
"I played good, just fell a little short again. It was Jon played a great round of golf, four under today on that golf course is a really good score."