Wimbledon 2018: Sloane Stephens makes surprise first-round exit after defeat by Donna Vekic

Vekic beat Sloane Stephens, the world No 4 and US Open champion, 6-1, 6-3 to register the first win of her career over a top five opponent

Donna Vekic had been unable to sleep after watching Croatia’s dramatic penalty shoot-out victory over Denmark in the World Cup the night before, but the world No 55 stayed awake long enough in the opening match on Court One to record one of the biggest victories of her career here on Monday.

Vekic beat Sloane Stephens, the world No 4 and US Open champion, 6-1, 6-3 to register the first win of her career over a top five opponent. The 22-year-old Croatian had recorded three previous victories over seeded opponents in Grand Slam competition, but had never claimed as significant a scalp as that of Stephen's.

The victory also helped to ease the memory of high-profile defeats that Vekic had suffered here in her last two visits. Two years ago she lost to Venus Williams in the opening match on Court One and last year she was beaten by Johanna Konta in one of the matches of the tournament, the Briton winning the deciding set 10-8.

Vekic had prepared for her latest big-match outing at the All England Club by watching Croatia’s nervous World Cup victory the previous evening. “Oh my God,” she said when asked what she had thought of the match. “That was crazy. I couldn’t sleep after that.”

Vekic’s boyfriend is Switzerland’s Stan Wawrinka, who was playing the third match of the day on Centre Court. Vekic said she was hoping for a World Cup semi-final between Switzerland and Croatia.

Two of the five tour-level finals in which Vekic has played have been on grass. The world No 55 won the title in Nottingham last year and was runner-up at Edgbaston in 2013.

“I think grass really suits my game,” she said. “I try to play aggressively. My serve wasn’t working quite as well today. I had a couple of double faults, but I’ll work on that tomorrow and hopefully I’ll serve better in my next match.”

Vekic needed just 71 minutes to complete her victory over Stephens. Although the Croatian served nine double faults, it was Stephens who kept struggling to hold serve. Vekic had 17 break points in the match and converted six of them, while Stephens made too many errors.

“We were both struggling at the beginning because it was very windy,” Vekic said. “It was tough to get some rhythm going. But I thought that towards the end the level of tennis was really high.”

The US Open champion has made an early exit here at Wimbledon (Getty Images)

Vekic said she did not regard the win as the biggest of her career. “It’s only the first round and I would like to go further in the tournament,” she said.

Stephens had arrived here with an outside chance of finishing the fortnight as the world No 1. Having won her first Grand Slam title at last year’s US Open, she also reached the final at last month’s French Open before losing to Simona Halep.

The American was philosophical in defeat. “We play a very long season,” she said. “There’s no one that is going to win every single week. Even the No 1 player in the world loses. It happens.

“Sometimes people do overreact, say I need a new coach, new physio, whatever it is. I do believe that if you just work on yourself and focus on yourself, you’ll allow yourself to have success, no matter what else is going on around you.”

Stephens said she had found the transition from clay to grass difficult but insisted: “Everyone is dealing with the same conditions, so it’s not just me.”

She added: “I thought my preparation was good. I had a good training block after the French. I did more than I would normally do. I came in here feeling not too bad. I thought I’d have not a great tournament, but I was feeling good about myself and the way I was playing.”

Caroline Wozniacki booked her place in the second round (Getty)

Asked what made Vekic such a good grass-court player, Stephens said: “She hits very flat, which works on grass. All of her shots are pretty flat. She has a decent serve. It works. When you put a couple of good patterns together and execute your game properly, obviously anyone can play well, but grass I think suits her game better.”

Another American appeared to be in danger of an early exit when Venus Williams lost the first set to Sweden’s Johanna Larsson, but the five-times champion recovered to win 6-7, 6-2, 6-1. Williams, who at 38 is the oldest woman in the draw, misfired regularly in the first set but won 10 games in a row from 2-1 down in the second.

Caroline Wozniacki, who warmed up for Wimbledon by winning the Nature Valley International in Eastbourne, eased into the second round by beating Varvara Lepchenko 6-0, 6-3 in just 59 minutes. Although she has never gone beyond the fourth round here, Wozniacki is a former Wimbledon junior champion.

Magdalena Rybarikova, who made the semi-finals here last year, became the first seed to go out of the tournament when she was beaten 7-5, 6-3 by Romania’s Sorana Cirstea.

Elina Svitolina, the world No 5, had won all 11 of her matches in 2018 against opponents ranked outside the world’s top 50 but was beaten 7-6, 4-6, 6-1 by Germany’s Tatjana Maria, the world No 57. Svitolina has rarely performed at her best on grass, while Maria arrived here fresh from winning the first singles title of her career at the Mallorca Open.