Top seed Roger Federer beat Germany's Mischa Zverev 7-6(4), 6-4 to advance to the last eight of the Halle Open on Thursday as the 18-times grand slam champion sharpens his grasscourt game ahead of Wimbledon.
Federer, who skipped the entire clay court season after winning the Australian Open and claiming titles at Indian Wells and Miami this year, will next play defending champion Florian Mayer who beat Frenchman Lucas Pouille in three sets.
The Swiss, who lost his first comeback match in Stuttgart last week, is still lacking some game sharpness and squandered three set points at 5-4 in the first set of an entertaining serve-and-volley encounter.
He persisted and carved out two more, winning the tiebreak by whipping a crosscourt backhand winner on his fourth set point.
Zverev's erratic first serve was a liability and Federer pounced again at 4-4 in the second set to break the German, whose younger brother Alexander is through to the quarter-finals, and served out the match.
World number nine Kei Nishikori's own Wimbledon preparations suffered a setback when he was forced to retire injured for the third straight time at this tournament.
The third seed needed to take a medical time-out against Karen Khachanov to treat a back injury before playing on for a few points and retiring with the Russian leading 3-2 in the first set.
Wimbledon, the only grand slam to be played on grass, starts on July 3.
Khachanov will now play fellow Russian Andrey Rublev, who earlier beat Mikhail Youzhny.
Cilic and Querrey march into Queen's quarter-finals
The top seeds have been scattered but Marin Cilic and Sam Querrey continued the charge of former winners at the Aegon Championships on Thursday as they reached the quarter-finals.
With Bulgarian Grigor Dimitrov having already progressed, three former champions are among the last eight at the prestigious pre-Wimbledon grasscourt event at Queen's Club.
Fourth seed Cilic, winner in 2012, overpowered American teenager Stefan Kozlov 6-0, 6-4 while Querrey, who triumphed seven years ago at the west London club, got the better of Australian Jordan Thompson, winning 7-6(3), 3-6, 6-3.
Russian Daniil Medvedev beat fellow 21-year-old Thanasi Kokkinakis who failed to match the heights he reached when beating third seed Milos Raonic in round one, losing 6-2, 6-2.
Medvedev will face 2014 winner Dimitrov on Friday.
Spanish veteran Feliciano Lopez continued the form he showed in reaching the Stuttgart grasscourt final last week with a 6-1, 7-6(4) defeat of French qualifier Jeremy Chardy and will face Czech Tomas Berdych for a place in the semi-finals.
Cilic now looks favourite for the title, especially after the clinical way he dispatched 19-year-old Kozlov with his serve and forehand almost unplayable at times.
Cilic, who beat John Isner in round one, will now take aim at his third American in a row in the quarter-finals when he takes on unseeded Donald Young.
Konta and Svitolina exit at Birmingham event
Britain's Johanna Konta crashed out of the Aegon Classic in the second round on Thursday, suffering a 6-1, 6-3 loss to impressive American Coco Vandeweghe at the event in Birmingham, England.
Second-seed Elina Svitolina of Ukraine was also knocked out after suffering a surprise three-set defeat by Italian qualifier Camila Giorgi.
Vandeweghe dominated the first set with her strong serve too much for fourth seed Konta as she wrapped up the set in 24 minutes.
Konta, the world number seven, improved in the second but never truly looked like mounting a comeback against the 25-year-old Vandeweghe, who was a Wimbledon quarter-finalist in 2015.
Vandeweghe faces Garbine Muguruza in the quarter-finals on Friday after the Spaniard's 6-1, 6-4 win over American Alison Riske.
Giorgi won six of the last seven games to triumph 6-4, 4-6, 6-2 over Svitolina, who said she was hampered by a sore foot. The 25-year-old Italian will meet Australian Ashleigh Barty in the last eight.
France's fifth-seeded Kristina Mladenovic had to work hard to get past China's Shuai Zhang 6-4, 7-6(3) and set up what looks a fascinating quarter-final against Czech Petra Kvitova.
Azarenka's return cut short in Mallorca
Former world number one Victoria Azarenka's return from maternity leave was cut short by young Croatian Ana Konjuh at the Mallorca Open on Thursday.
The Belarusian, who saved match points in her first-round victory against Japan's Risa Ozaki, went down 6-1, 6-3 to the seventh seed on the grasscourts at Santa Ponsa.
Konjuh, 19, dominated from the start and Azarenka had no answer to the depth and power of her opponent.
"I know Azarenka is coming back, but it's always tough to play against her," said Konjuh, who did not allow Azarenka a point until the third game of the match.
"She's one of the best players in the world.
"I was motivated for sure, and I'm really glad that I could play so well today and win."
Konjuh will face Anastasija Sevastova in the quarter-finals.
Italian Roberta Vinci also reached the last eight with a 6-4, 5-7, 6-2 win over Belgium's Kirsten Flipkens.
Defending champion Caroline Garcia's match against Jana Cepelova was suspended at 2-2 in the third set as the light faded.
Svitolina suffers injury scare ahead of Wimbledon
World No 5 Elina Svitolina has expressed fears that a foot injury that contributed to her Aegon Classic defeat to Italian Camila Giorgi in Birmingham on Thursday could lead to her withdrawal from Wimbledon.
The in-form Ukrainian won the Italian Open in May and lost in the French Open quarter-finals earlier this month but has never progressed past the second round at the All England Club.
Svitolina, 22, has never won a tournament on grass and says that withdrawing from Wimbledon could help her get a head start on preparations for hard court tournaments later this year.
"I was really looking forward to this year at Wimbledon. But today the court was slippery and it's so bad for my foot. I will do my best," Svitolina told reporters after the match.
"But for the moment it's very uncomfortable, and there is a question about it, because the season is still long and there is lots of big tournaments as well where I will feel more comfortable and confident on the hard court."
Svitolina joins a number of top players racing to be fit for Wimbledon, which begins on July 3, with Nick Kyrgios, Angelique Kerber, Simona Halep and Juan Martin Del Potro all withdrawing from warm-up tournaments for the third grand slam of the year.
