Swiss Stanislas Wawrinka stunned second seed David to reach the second round of the Zagreb indoor tournament.
The recall of a crushing loss might not have the same attraction as the memory of an inspired victory for most top tennis players, but World No 8 Stanislas Wawrinka wears failure as a badge of honour stamped permanently on his arm.
Australian Open champion Stanislas Wawrinka crashed to a shock second-round defeat at the Madrid Open on Tuesday when he was upset 1-6, 6-2, 6-4 by qualifier Dominic Thiem.
The parade of serial grand slam champions is reserved for Tuesday at the ATP World Tour Finals but the supporting cast provided compelling opening acts with Stanislas Wawrinka and Juan Martin del Potro in the spotlight.
Strong title contenders Marin Cilic and Stanislas Wawrinka were knocked out of the Chennai Open by their respective opponents on Friday.
World number three Stanislas Wawrinka fell at the first hurdle in the Dubai Open on Tuesday, beaten 7-6(4), 6-3 by 77th-ranked Bosnian Damir Dzumhur.
Zverev has not lost to Wawrinka in two previous meetings but is not taking the 2014 Melbourne Park champion lightly.
Former World No 1 Azarenka, the winner of two Australian Open titles and twice a US Open runner-up, withdrew from last year's tournament at Flushing Meadows because of a child custody battle.
Rafael Nadal fought off a ferocious challenge from Stanislas Wawrinka to earn his second Group A victory at the ATP World Tour Finals on Wednesday and guarantee ending 2013 as world number one.
Australian Nick Kyrgios let his tennis do the talking against Stanislas Wawrinka as he knocked the fourth seed out of the Madrid Open with a scintillating display on Wednesday.
Six times a men's singles champion Down Under, the Serbian will be joined in making a return at MelbournePark by 2008 women's champion Maria Sharapova, who missed last year's tournament because of a doping ban.
Factbox on Rafael Nadal's French Open final wins
Change might be afoot though, according to American great John McEnroe
With temperatures reaching almost 38 degrees on court, Murray, a twice Wimbledon champion, was beaten 7-6(4), 6-2 by Australian world number 90 Jordan Thompson.
With 1,500 points available for an undefeated champion next week, the tournament could produce a thrilling climax with Murray and Djokovic, who have never met at the O2, facing off in the final for the year-end number one ranking.
Former world number one Rafael Nadal displayed more signs of a return to top form with a ruthless 6-2, 6-1 hammering of Stanislas Wawrinka to reach the semi-finals of the Shanghai Masters on Friday.
German seventh seed Alexander Zverev recovered from a slow start to beat former champion Stan Wawrinka 1-6, 6-3, 6-4, 6-2 in the Australian Open on Wednesday to reach his first career Grand Slam semi-final. Swiss Wawrinka, who won the first of his three Grand Slams at Melbourne Park in 2014, broke Zverev twice early in the opening set to breeze through the opening set but the 22-year-old German came roaring back into the contest.
For good reason a two-week Grand Slam can be described as a 'last man standing' marathon of mental and physical endurance, which makes Roger Federer's haul of 19 all the more incredible.
Novak Djokovic sauntered past Spaniard Feliciano Lopez to reach the quarter-finals of the Shanghai Masters on Thursday but Andy Murray had to claw past big-serving American John Isner after losing a first-set tiebreaker.
Belgium's Elise Mertens rallied from a set down to beat top seed Simona Halep 3-6, 6-4, 6-3 and clinch her first Premier-level title at the Qatar Open on Saturday.
For 15 minutes Novak Djokovic appeared to have a fight on his hands at the ATP World Tour Finals on Wednesday, then the Serb dialled up his A game and tore Stanislas Wawrinka to pieces.
The 29-year-old Frenchman crashes 'top-four' party to set up semi-final against World No Djokovic
Simona Halep and Stan Wawrinka beat the heat with straight-sets wins to reach the third round of a sweltering US Open on Thursday while American hope Jack Sock wilted under the punishing conditions, collapsing on court.
Images from Day 8 of the Australian Open at Melbourne Park on Monday.
Top 10 seeds David Ferrer, Tomas Berdych, Stan Wawrinka and Richard Gasquet raced into the second round of the Australian Open on Monday, apparently eager to make the most of relatively mild conditions at Melbourne Park.