The top seed is out of the ASB Classic tennis tournament.
In what was his opening match in Auckland after a first round bye, Italian Fabio Fognini gave up a one-set lead in a second round loss to Spain's Feliciano Lopez on Wednesday.
The world No 12 went down 6-3 4-6 3-6 to the 61st ranked Spaniard.
It was an impressive effort from Lopez, who is not only 38 but was playing his second match of the day.
On Wednesday morning he had been on court for almost two-and-a-half hours in a 3-6 7-6 6-4 win over fellow Spanish player Pablo Andujar.
Lopez will face Hubert Hurkacz in the quarterfinals, after the Polish sixth seed was a 6-2 7-6 victor over Swedish qualifier Mikael Ymer.
Fognini's exit means young Canadian star Denis Shapovalov became the tournament's highest ranked remaining player.
First up in Wednesday's night session, the 20-year-old Shapovalov, the world No 13, was too strong in a 6-4 7-6 win over countryman Vasek Pospisil.
In the match that followed, another big name fell as third seed Karen Khachanov suffered an upset loss to John Millman.
The powerful Russian world No 16 took the first set 6-4 but the plucky Australian, ranked down at 47, rallied back to progress 4-6 6-3 6-3.
Millman faces a quarterfinal against French fifth seed Benoit Paire, who came from behind for a 4-6 6-4 6-3 victory over Brazil's Thiago Monteiro.
Earlier on centre court, John Isner was happy to get the winning feeling back.
A two-time champion in Auckland and the fourth seed this year, the big serving 34-year-old was the first player to advance to the quarterfinals.
Isner scored a hard-fought 7-6 6-7 6-3 win over fellow American and the tournament's defending champion Tennys Sandgren.
The result comes after Isner went down in all three of his matches at the ATP Cup event in Australia last week and he hoped it would help put those losses out of his mind.
Thanks to Tuesday's rain, Italian Andreas Seppi had to complete his first round clash on Wednesday morning, coming from behind for a 3-6 6-4 6-4 victory over Frenchman Adrian Mannarino.
But he was unable to replicate that against Kyle Edmund, the Brit setting up a quarterfinal against Isner with a 6-3 7-6 win.
Marco Cecchinato was the other player who faced with two singles matches in one day.
The Italian eventually won his first round match in a 7-6 6-7 7-6 epic against Argentinian Leonardo Mayer which lasted more than three hours.
Cecchinato also couldn't back up, though, losing in straight sets in the afternoon to Ugo Humbert, of France.
Meanwhile Artem Sitak came out on top in the battle of two of New Zealand's leading doubles players.
Sitak and Indian's Divij Sharan won a pair of tie-breakers to beat Michael Venus and Australian partner John Peers 7-6 7-6.
Marcus Daniell was the other New Zealander to advance in the doubles.
Daniell and Austrian Philipp Oswald won the first set 6-3 against Fognini and countryman Simone Bolleli, before Fognini was forced to retire at 1-1 in the second set.