Rafael Nadal admitted his 6-4, 6-4 loss to Germany's Alexander Zverev in the Madrid Open quarter-finals on Friday was a "step back" but insisted there were plenty of positives as he plots his way to a 14th Roland Garros title.
Nadal has now fallen early in two clay-court Masters tournaments ahead of the Grand Slam in Paris, after going out in the Monte Carlo quarter-finals last month before winning in Barcelona.
Even in Barcelona, however, he needed to save a championship point to beat Stefanos Tsitsipas in the final.
Nadal is hoping to clinch a 14th Roland Garros title and record-setting 21st major in the French capital next month.
"I took steps forward, but when you go up a staircase, there are times when it happens that you take a step back, that's what happened today," said five-time Madrid champion Nadal.
"It's a week where there were a lot of positive things. I'm leaving Madrid with good feelings in general, and the bad one having played a match like today.
"Now, what is the goal before Roland Garros? Go to Rome (for next week's Italian Open) and win, that's all."
Nadal had been hoping to reach the semi-finals of a Masters event for the 75th time.
"I had the match under control at the beginning and was playing well for six games, probably playing better than him," said the Spaniard.
"Then at 4-2 serving for 5-2, I had a disaster."
Nadal continued: "Of course, playing against one of the best players in the world, under these circumstances, with this speed of the court, it's very difficult."
Zverev has beaten Nadal three times in a row but this was his first victory on clay against the world number two.
"It's definitely one of the biggest wins of my career so far, especially on clay against Rafa," Zverev said.
"It is the toughest thing to do in our sport. Beating him in his house, in Spain, is incredible."
Zverev's impressive straights-set win at the Caja Magica earns him a meeting with Dominic Thiem in the semis, in what will be a repeat of last year's US Open final, which was won by Thiem.
After losing to world number eight Andrey Rublev in Monaco, Nadal was convincingly beaten by Zverev and the spotlight will be on the 34-year-old now in Rome next week, his last tournament before heading to Paris.
- Thiem in fourth Madrid semi -
It started well for Nadal when he broke Zverev to love to lead 4-2 in the first set, Zverev serving a double fault to give away the first advantage.
But the world number five immediately hit back and then pulled away, four straight games clinching him the set.
A whipping forehand down the line put Zverev up another break midway through the second and while Nadal resisted more pressure in the seventh game to hold, Zverev served out an impressive victory after an hour and 44 minutes.
Thiem had earlier come from a set down to beat 36-year-old John Isner of the United States 3-6, 6-3, 6-4 and reach the last four.
"He's one of the best servers in history, especially here in the altitude, it bounces high and it's so difficult to return," said Thiem after reaching the Madrid semi-finals for the fourth successive time.
Norway's Casper Ruud reached the semi-finals of a claycourt Masters event for the third successive time by beating Alexander Bublik of Kazakhstan 7-5, 6-1.
Ruud, who knocked out world number five and Monte Carlo Masters champion Stefanos Tsitsipas in the previous round, will face Matteo Berrettini for a place in the final.
Italian world number 10 Berrettini defeated Chile's 25th-ranked Cristian Garin 5-7, 6-3, 6-0 to reach a second Masters semi-final.