Alexander Zverev said he was "s******* my pants" as he attempted to stave off a fightback from Carlos Alcaraz in his French Open quarter-final win on Tuesday.

Zverev claimed an impressive 6-4 6-4 4-6 7-6 (9-7) win over the 19-year-old Spaniard to set up a semi-final with either Novak Djokovic or Rafael Nadal.

The German initially appeared dominant as his controlled and composed display saw him take a two-set lead, and although Alcaraz did improve in the third, Zverev even had the opportunity to serve out the match for a straight-sets win.

He failed to grasp that chance and Alcaraz looked likely to level the match as he began to exert greater control in rallies – his dropshots proving especially threatening.

But Zverev clung on even as the crowd vociferously backed his opponent in the fourth-set tie-break, eventually seizing his opportunity when he felt Alcaraz was potentially taking charge of the match.

Asked about his emotions in a fourth set that was something of a rollercoaster, he said: "[I was] s******* my pants as well."

The rather crude joke received a flat response from a Court Philippe-Chatrier crowd that never particularly got behind Zverev.

However, he soon waxed lyrical about his popular opponent, who was the first top-10 scalp of Zverev's career at a grand slam.

"At the end of the day, I knew I had to play my absolute best tennis from the start, and I'm happy I did that," Zverev continued.

"He kept on coming back, he's an incredible player. I told him at the net that he's going to win this tournament a lot of times, not only once.

"So I hope I can win it before he starts beating us all and we'll have no chance at all."

Zverev suggested his dip after the second set was contributed to by the changing conditions, having thrived in the sun and then seen his level drop when in the shade.

But he could not hide his joy at avoiding a fifth set.

"For me, when it's shady and slower it's not perfect for me," he said. "I didn't get broken once when it was sunny, the ball was a lot faster, I had to adjust my strings as well.

"The match was turning his way, so at the end of the day I'm extremely happy I won the tie-break and I didn't have to play a five-set match, didn't have to be disappointed after the five-set match again like I was last year.

"I'm still in the tournament – usually I'm a very good talker, but right now I can't talk. I'm speechless."