World Number 2 Novak Djokovic recovered from a set down to defeat fellow Serb Viktor Troicki 3-6, 6-4, 6-2 in the second round of the Dubai Championships on Wednesday.
But third seed Andy Murray slumped to a shock 7-6, 4-6, 6-4 defeat by Serb Janko Tipsarevic and fourth seed Nikolay Davydenko had to retire with a wrist injury while trailing German Michael Berrer 6-3.
Former Australian Open finalist Jo-Wilfried Tsonga, seeded fifth, also went down 7-5, 6-3 to Croatian Ivan Ljubicic.
Djokovic struggled to adjust to the afternoon heat, having won a night-time first-round tussle with Spain's Guillermo Garcia-Lopez on Monday.
"He (Troicki) was the better player in the first set and a half and I was struggling a lot," Djokovic said at courtside. "He was serving well and the balls were going very fast. There's a big difference playing at night and in the day."
Troicki took the first set after breaking his childhood friend's serve in the first and ninth games, but Djokovic responded, dropping only one point on his first serve in the second set.
Having broken Troicki, the 2008 Australian Open winner squandered four set points against serve at 5-3, before squaring the match in the next game with a ferocious forehand winner down the line.
Djokovic raced into a 4-0 final-set lead, eventually clinching victory with a big serve. He will play Ljubicic in Thursday's quarter-finals.
SWOLLEN WRIST
World No 4 Murray, in only his second match since losing the Australian Open final to Roger Federer in January, rallied from 5-2 down in the final set to serve to square the contest against Tipsarevic.
The Serb though earned a deserved third career victory over the twice grand slam finalist with a confident smash.
The Briton said he was not too disappointed after using the Dubai event to try a more aggressive serve and volley approach.
"The first set I played a very different game, trying to get forward and work on some different things," said Murray.
"I think it was a good learning experience - if it was a slam, my tactics would have been different. I wasn't coming in as well prepared as I have done in previous tournaments."
Russian Davydenko looked out of sorts against Berrer, losing the first set 6-3, having battled back from a set down on Tuesday to get into the last 16.
"It started yesterday afternoon," said Davydenko. "I was thinking: 'Okay there's pain, but I will recover'. I warmed up (today) and the wrist was feeling okay but the match was different and it started to get swollen."
The World No 6 is now a doubt for Russia's Davis Cup tie against India in Moscow next week.
Berrer will now play Marcos Baghdatis after the Cypriot defeated Indian qualifier Somdev Devvarman 6-3, 3-6, 6-1.
Austria's Jurgen Melzer beat Spaniard Tommy Robredo 6-3 7-5 to earn a last-eight clash with Marin Cilic after the world number nine had a routine 6-2 7-6 victory over another Austrian, Stefan Koubek.
Croatian Cilic was rarely at his best, making only 47 percent of first serves, but he appeared confident of progressing beyond the quarter-final stage, having won two tournaments already this year.
"With winning a lot, you are believing in yourself," the 21-year-old said.
