Sam Querrey’s hot hard court form continues with the American dumping second seed Kei Nishikori out of the Abierto Mexicano Telcel 6-4, 6-3 on Wednesday night. Having captured an eighth ATP World Tour title in Delray Beach on Sunday, the 27 year old snapped a four-match losing streak against the World No. 6 in the Emirates ATP Rankings.

The win puts Querrey through to his third straight ATP World Tour quarter-final and ensured the Acapulco tournament was without its top two seeds after David Ferrer’s earlier defeat to Alexandr Dolgopolov.

Nishikori was coming off a title run of his own in Memphis less than two weeks ago. It marked the first time in four ATP World Tour events this year the Japanese player did not reach at least the quarter-finals.

“It’s always hard when you play against good players, but it wasn’t my day today,” Nishikori said. “There were many things that I should do better, especially my serve and I wasn’t going for enough, my groundstrokes, my forehand especially, I was missing a lot, so I wasn’t aggressive enough to beat Sam today. Also he was hitting really big serves so there weren’t many chances for my return game.”

Querrey sent down eight aces and dropped just four points when his first serve found the mark. He will next face fellow American Taylor Fritz after the 18 year old – who will become the youngest player to crack the Top 100 in next week’s Emirates ATP Rankings – overcame an age gap of 17 years to beat Victor Estrella Burgos of the Dominican Republic 6-1, 6-3. Fritz claimed 75 per cent of first-serve points and broke five times to progress in one hour.

Seventh seed Grigor Dimitrov also moved safely through to the quarter-finals on Wednesday night, with the 2014 champion posting a routine 6-3, 6-4 result against Donald Young. The Bulgarian notched his fifth win in six FedEx ATP Head2Head clashes against the American, claiming 78 per cent of first-serve points and saving seven of eight break points in the one-hour, 26-minute affair.

Alexandr Dolgopolov had not beaten a Top 10 player in the Emirates ATP Rankings since last fall, but he ended the drought with a comprehensive 6-4, 6-4 win over defending champion David Ferrer in the second round of the Abierto Mexicano Telcel event in Acapulco on Wednesday. The flashy Ukrainian hit 22 winners and overcame a late Ferrer challenge to move into his third quarter-final of the year.

Dolgopolov came into the match trailing 2-8 in his FedEx ATP Head2Head rivalry against the consistent Spaniard, but took command of the match from the baseline and secured his ninth win (9-36) against a player in the Top 10. His best showing in Acapulco came in 2011 and 2014, when he reached the semi-finals.

Fifth seed Bernard Tomic overcame Adrian Mannarino 6-4, 6-4 to move into the quarter-finals. The Aussie won in 71 minutes and remains perfect against the French left-hander (3-0 at tour-level).

Three of the top four teams in the Dubai doubles draw were eliminated in the first round on Wednesday. Jamie Murray and Tommy Robredo, teaming for the first time, fought past No. 4 seeds Henri Kontinen and John Peers 2-6, 6-4, 10-8. The unseeded duo dropped serve twice in the opening set, but did not face a break point the rest of the way and won in 76 minutes.

Top seeds Jean-Julien Rojer and Horia Tecau were upset by Feliciano Lopez and Marc Lopez. The Spaniards saved nine of 10 break points faced to win in 76 minutes. Also eliminated were second seeds Rohan Bopanna and Florin Mergea. Daniel Nestor and Radek Stepanek topped the Indian-Romanian duo 3-6, 7-6(6), 10-4, winning 69 points to their opponents’ 68.

Rising stars Hyeon Chung and Jiri Vesely beat veterans Roberto Bautista Agut and Joao Sousa 6-7(2), 7-6(6), 11-9. The youngsters, who needed to qualify for the main draw, pulled out the win in one hour and 53 minutes.

Second seed Stan Wawrinka finished strongly to beat qualifier Franko Skugor 7-5, 6-1 on Wednesday night in the second round of the Dubai Duty Free Tennis Championships.

Playing in his first tour-level match in nearly six years, Skugor gave Wawrinka a stern test in the first set before eventually losing serve in the 12^th game. After making the breakthrough, Wawrinka raced to the finish line, wrapping up victory in 83 minutes.

“I think it wasn’t amazing, but it’s a good win,” said Wawrinka, who was two points from defeat against Sergiy Stakhovsky in the first round on Tuesday. “Happy to get through to playing in the quarters tomorrow, winning in two sets tonight. There’s a lot to improve, but in general I’m happy to win.”

The 30-year-old Wawrinka is chasing his second ATP World Tour title of the season, after victory in Chennai (d. Coric), and goes on to face Philipp Kohlschreiber, who defeated Borna Coric 6-2, 7-6(5) in one hour and 31 minutes.

Wawrinka leads their FedEx ATP Head2Head series 2-0, but it will be their first meeting since 2008.

“It’s going to be an interesting match,” said Wawrinka. “He’s been there, Top 30, for many, many years. He’s always a tough player, always beating some good players during the year.

“You need to play solid and a good match to beat him. He’s not going to give you the match. Generally he’s playing his level every time. I will have to serve well, play my game and go for it.”

World No. 1 Novak Djokovic notched his 700th tour-level win in style on Wednesday night as he defeated Malek Jaziri 6-1, 6-2 to reach the quarter-finals of the Dubai Duty Free Tennis Championships.

The Serb cruised to victory in 65 minutes, before he was presented on court with a commemorative cake to celebrate his achievement. He is only the 12th player in the Open Era (since 1968) to hit the 700 singles victories mark.

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The 28-year-old Djokovic is a four-time champion at this ATP World Tour 500 hard-court tournament and is looking to reclaim the title he won in 2009 (d. Ferrer), 2010 (d. Youzhny), 2011 (d. Federer) and 2013 (d. Berdych).

The Belgrade native goes on to face Feliciano Lopez, who was a 6-3, 7-6(7) winner over Lukas Rosol. Djokovic is unbeaten in his seven previous meetings with the left-handed Spaniard, who himself is a two-time finalist in Dubai. Lopez finished runner-up in 2004 (l. to Federer) and 2008 (l. to Roddick).