Rafael Nadal crashed out to Fabio Fognini in the Monte Carlo Masters semifinals on Saturday, going down 6-4, 6-2.
The shock result leaves Italian 13th seed Fognini facing unseeded Serb Dusan Lajovic in Sunday’s unscripted final.
“I played one of my worst matches on clay in 14 years,” said Nadal. “It’s difficult to find any positives – I deserved to lose.”
Fognini, who beat Nadal twice on clay in 2015, stopped a 25-set win streak in the principality for the world No 2.
For the 31-year-old Italian, based just over the border in San Remo, it was a fourth career win over Nadal and third on clay.
“I had a really good week, did some good work,” said the Italian.
“I was born near here, I know how to play on clay. This will be the final that no-one expected, I just hope to recover well and be ready.
“Plus Lajovic is trained by my ex-coach – we laughed about that in the locker room.”
Fognini, cheered by thousands of compatriots on Centre Court, broke Nadal three times in a 55-minute opening set.
Nadal saved three match points while trailing a set and 5-0 as he broke Fognini in a last-gasp effort.
But the 13th seed would not be denied, earning another pair of chances in the eighth game and claiming victory with a forehand winner down the line.
“I’m calm, I want to enjoy my victory,” Fognini said after reaching his first final at the Masters 1000 level.
“I’ve beaten Rafa on clay, I’m really happy, it was windy and tough to play.
“Of course it’s a surprise to play Lajovic, but he’s playing good.”