Carlos Alcaraz believes he will only improve on grass after struggling past French journeyman Arthur Rinderknech in the first round at Queen's Club on Tuesday.

The world number two was playing only his seventh match on the surface and his first outside of Wimbledon as he prepares for the third Grand Slam tournament of the season next month.

Lucky loser Rinderknech only found out he was playing the Spaniard hours before the match after Frenchman Arthur Fils, Alcaraz's scheduled opponent, withdrew from the tournament.

But the 27-year-old almost stunned the US Open champion before Alcaraz edged through 4-6, 7-5, 7-6 (7/3) in just over two-and-a-half hours.

"It has been a really tough match, he has played four or five matches on the grass and this was my first one," said Alcaraz.

"It was really difficult to adapt my game to the grass. For me it's tough to play here, but Queen's is a tournament I really wanted to play."

Alcaraz was playing his first match since losing to Novak Djokovic in the semi-finals at the French Open and is hoping to improve once he gets accustomed to the conditions.

"I couldn't play tennis on grass at home but I practised the movement on grass. I practised here a little bit before the tournament and I felt really good, even though it was the first match.

"I would say I'm going to be better in the next round."

Alcaraz will face Czech Jiri Lehecka in the second round.

Second seed Holger Rune was also pushed by American Maxime Cressy before the Dane progressed 7-6 (7/4), 7-6 (7/3) to secure his first ever grass court win on the ATP Tour.

World number 10 Frances Tiafoe was more comfortable as he saw off Botic van de Zandschulp 6-2, 6-4 to continue his winning streak after lifting the title in Stuttgart last week.

kca/jc