The rivalry between Tiger Woods and Phil Mickelson was one of golf’s most exciting, but for a time in the early 2000s, there was no doubt about who was on top. Woods was the sport’s premier athlete, and in the opinion of his longtime rival, it came with a level of domination that will be “unrepeatable” for present and future stars.

“I don’t think anybody today who wasn’t there to witness it, and I don’t think anybody before, will ever see that level of play again,” Mickelson said Tuesday at TPC-Sawgrass, via ESPN.

Woods took the golfing world by storm after winning the 1997 Masters and proceeded to win 14 majors over the next 11 years. His signature win came at the 2000 U.S. Open, where he won by a record-setting 15 strokes. He was named PGA Tour Player of the Year five consecutive years from 1999 to 2003.

Mickelson called it the greatest golf that “has ever been played.”

“It was the most remarkable golf in the history of the game, and I think unrepeatable,” Mickelson said. “I think it was that good. I look at 2000 as being kind of the benchmark at the U.S. Open and being the greatest golf I’ve ever witnessed and I believe has ever been played.”

“And it sucked to have to play against him. It really did. You look at it and say, ‘How am going to going to beat this?’ There was a stretch there for a numbers of years that it was so impressive that it was hard to imagine that it was actually happening, that he was hitting some of the shots that he was hitting and playing that well.

“The guys today look back and they say, ‘Come on, how much better could he have been?’ and so forth. And it goes to show you that they weren’t there to witness it.”

Woods, now 42, has not won a tournament since 2013, but he’s been competitive on the tour for the first time in years. From 1997 to 2013, he won 79 PGA Tour events, which is second all-time behind Sam Snead’s 82 wins. He’s also second all-time in majors behind Jack Nicklaus’ 18, a figure that once seemed easily attainable for Woods but now is unlikely to be passed anytime soon.

Mickelson couldn’t keep up with Woods in the early 2000s, but emerged as one of his biggest rivals by winning the Masters in 2004, 2006 and 2010. He also won the 2005 PGA Championship and 2013 Open Championship.

However, Mickelson never finished higher than second in the World Golf Rankings, despite being in the top five for years. Woods’ hold on the top spot was a big part of that.