It was a day to remember for the Croatian veteran, who booked his spot in the second round of the Indian Wells Masters and set a new ATP record.
Ivo Karlovic became the first player aged 40 and over to win an ATP Tour match since 1995 following his opening-round victory at the Indian Wells Masters.
Croatian veteran Karlovic – who celebrated his 40th birthday on February 28 – edged Matthew Ebden in straight sets on Thursday.
Karlovic became the first 40-year-old since Jimmy Connors in Halle 24 years ago to win on the Tour.
Prajnesh Gunneswaran, meanwhile, enjoyed a memorable ATP Masters 1000 debut against Benoit Paire.
Karlovic defying Father Time
Making his 14th Indian Wells appearance, Karlovic outlasted Ebden 7-6 (7-3) 7-6 (7-3).
Karlovic – who became the oldest ATP Tour finalist since 1977 in Pune this year – fired down 18 aces in a match lasting one hour, 49 minutes.
A 2011 Indian Wells quarter-finalist, Karlovic will meet countryman Borna Coric in the second round.
Gunneswaran stuns Paire
The 29-year-old upstaged former world number 18 Paire 7-6 (7-5) 6-4 for just his second main-draw victory.
Making his first appearance in a Masters main-draw match, Gunneswaran was too good for the Frenchman as he booked a second-round clash with Nikoloz Basilashvili.
He saved five of eight break points against Paire, who had a first-serve percentage of just 38.
Giron shocks Chardy
Another qualifier, Marcos Giron, produced one of the biggest upsets of the day.
Giron stunned Jeremy Chardy 7-6 (7-3) 7-6 (7-1) in his Masters debut on Thursday.
Jordan Thompson will meet Dominic Thiem in the second round after surviving a three-hour marathon against Federico Delbonis 6-4 6-7 (6-8) 7-6 (7-5) for his maiden Masters triumph, while Leonardo Mayer beat Reilly Opelka in straight sets.