Rafael Nadal moved to within one win of a 10th Barcelona title on Saturday when he swept past Argentina's Horacio Zeballos 6-3, 6-4 in the semifinals of the clay court event.
World No 5 Nadal, who captured a 10th Monte Carlo Masters last weekend, will face Dominic Thiem in the final after the Austrian stunned world No 1 Andy Murray 6-2, 3-6, 6-4.
Nadal, 30, who will be playing in his 106th career final on Sunday, won the Barcelona title in 2005-09, 2011-13 and 2016.
Despite his straight sets win, on a centre court which is named after him, Nadal was far from pleased with his week's work in the Catalan capital where rain has made the conditions heavy.
"In weeks like this, the one who manages to cope with the conditions we've had, which have been significantly different (than normal), is the one that survives," said the Spaniard.
"They aren't the best conditions for me and against Zeballos it wasn't easy at all. He took me out of my comfort zone, particularly in the first few shots of the rally which is what did damage."
Nadal will take a 2-1 career record over Thiem into Sunday's final with all their meetings having come on clay.
"Thiem combined some brilliant shots with some errors against Andy. It will be difficult, he is one of the best players in the world on clay," he added.
Thiem fired 41 winners and six aces as the fourth seed advanced to his 12th ATP World Tour final with a first win over Murray.
"It's the first win over a World No 1, so it's really something special," said Thiem who added it would "be a great honour to play Nadal".
"But it's also the first win over a Top 10 guy this season. There are many positive things to take from today's match.
"For me personally, it's the best victory this year so far. I went down in the third set when he broke me in the first game. But the way I came back mentally was a huge step forward today."
Murray squeezed past Albert Ramos-Vinolas in a three-hour encounter on Friday and looked flat-footed as Thiem roared through the opening set with three breaks of serve in just over half an hour.
The Scot had to stave off another break point in a marathon opening game to the second set.
But he held on and then jumped at his chance to break for 5-3 before serving out to take the match to a decider.
Murray, though, still looks a pale shadow of the player that rose to No 1 on a spectacular run at the end of last year as he struggles for form and fitness after an elbow injury.
Thiem had to battle back from a break down in the third, but constantly put pressure on the Murray serve and broke another three times in the deciding set to seal his place in the final.