Andy Murray knows he will have to be at his best again if he is to defeat Stan Wawrinka and reach the French Open final for the second consecutive year.
The pair also clashed in the last four a year ago, when Murray gave probably his best ever performance on clay to win in four sets before going on to lose to Novak Djokovic.
From unpromising beginnings, Murray has played his way into form and is through to a 21st grand slam semi-final.
While the world number one has dropped three sets, including the opener to Kei Nishikori in the quarter-finals on Wednesday, Wawrinka has romped through the draw.
The 2015 champion lost only seven games against in-form Marin Cilic in the last eight and has once again reserved his best for the biggest tournaments.
Murray said: "When we played last year, it was a similar situation coming in. I think Stan had played really well.
"I had struggled in some of my matches during the event last year, but I played one of my best clay-court matches that day to get the win. I need to do the same again.
"He's obviously played extremely well the last few years at the French, and he's confident. It's going to be very tough but I can learn some things from last year. I'm sure he will, as well, and will try to change some things. It should be an interesting match," he said.
After winning the tournament two years ago, Wawrinka fancied his chances of a repeat 12 months ago only to run into Murray at his most tactically and technically astute.
Wawrinka certainly gave the impression in Wednesday's press conference that he does not expect the same to happen again.
The 32-year-old, the oldest semi-finalist here since Jimmy Connors in 1985, believes Murray's shaky form prior to arriving in Paris can make this year a different story.
Wawrinka said: "I think he's probably a bit less confident. He's a bit more hesitant. Hopefully I can take advantage of that and find solutions to beat him.
"When you have a lot of wins behind you and confidence with your game, you can go for more. That's what he did last year, for sure.
"I expect him to try to do the same because that's always how he is trying to play against me, to be aggressive. But I think I will answer with my game. I think I'm playing better than last year, also. It can be only a big challenge and hopefully a good match," he said.
The second semi-final pits nine-time champion Rafael Nadal against Dominic Thiem, fresh from his upset of defending champion Novak Djokovic.
The women's final will be between title favourite Simona Halep and unseeded Jelena Ostapenko.
The Latvian and opponent Timea Bacsinszky were both playing on their birthday but it was Ostapenko who could celebrate after a 7-6 (7/4) 3-6 6-3 victory.
Third seed Halep defeated Karolina Pliskova 6-4 3-6 6-3 and goes into the final knowing victory would also give her the number one ranking.