Novak Djokovic apologised but confirmed he had been dealing with a blister after only playing a set of his exhibition match in Adelaide.
The world number one had reportedly withdrawn and was replaced by Filip Krajinovic for a clash against Jannik Sinner.
But Djokovic played the second set, winning it 6-3 after Krajinovic had taken the opener 6-3 on Friday.
The 17-time grand slam champion, who had a blister on his right hand, apologised after the match.
"I'm sorry that I didn't step in on the court from the beginning," Djokovic told Channel 9.
"I had to do some treatment with my physio and wasn't feeling my best the last couple of days, I didn't know how I'm going to react.
"I wanted to play and I wanted to get out here and hopefully it was enough for you guys to see all three of us performing in front of you on the court today, I hope you enjoyed."
Djokovic, who came out of hotel quarantine on Friday, said he could not pass up the opportunity to play in front of fans.
"It's not easy but it's part of what we do. We are professional athletes we learn over the years to play with the pain and it's just a question and case whether that pain is bearable or not," he said.
"Obviously coming off from the hard training block and having an ATP Cup and Australian Open around the corner you don't want to risk it too much.
"But the emotion was so strong in me to come out on the court today seeing almost full stands, I had to play, that's it, I had to play."
Djokovic is due to play the ATP Cup starting on Tuesday, before the Australian Open begins on February 8.
Murray knocked out of Geneva Open as Hanfmann books Djokovic clash
Andy Murray was denied a meeting with Novak Djokovic at the Geneva Open as Yannick Hanfmann completed a 7-5 6-2 win over the Scot on Tuesday.
Murray's first-round clash with Hanfmann was suspended due to rain on Monday, with the three-time grand slam champion 7-5 4-1 down.
He had earlier fumed at umpire Greg Allensworth as pollen rained down on the court in Switzerland, questioning why play had not been stopped.
The rain may have frustrated Hanfmann's victory pursuit on Monday, but it only provided a temporary reprieve for Murray as the players returned to complete the match the next day.
Hanfmann held his nerve through his final two service games to book a meeting with Djokovic for Wednesday.
In Tuesday's other early match, four-time grand slam quarter-finalist David Goffin was beaten in straight sets by Nicolas Moreno De Alboran.
The likes of Denis Shapovalov and Tallon Griekspoor are also in action in Switzerland on Tuesday, with Taylor Fritz and Casper Ruud joining Djokovic in entering for the second round on Wednesday.
Murray fumes at umpire amid severe weather at Geneva Open
Andy Murray fumed at the umpire as inclement weather forced his Geneva Open tie with Yannick Hanfmann to be suspended.
Murray's meeting with Hanfmann was postponed with the Scot a set and a double break down, with his German opponent in control at 7-5 4-1.
Former world number one Murray was furious with umpire Greg Allensworth as the weather closed in.
"I know you guys don't play but it'd be good to have a bit of a feel for what's happening," said Murray during a break in play.
"You're fine for us to play when there's s*** flying around?
"It's like it's snowing out here and you still want us to keep going."
Allensworth eventually sent the players into the dressing rooms.
Murray is aiming to use the Geneva Open to prepare for what is set to be his first French Open appearance since 2020.
A tie with Novak Djokovic is on the cards if Murray can turn things around on Tuesday, though it looks incredibly unlikely.
Zverev sees off Jarry to claim second Italian Open crown
Alexander Zverev claimed his second Italian Open title following a 6-4 7-5 victory over Nicolas Jarry in the final.
The German, who also triumphed in Rome seven years ago, captured his first silverware of the season - and sixth of his career in an ATP Masters event.
Having dropped just a single set on the way to his 11th Masters final, Zverev continued his impressive form by winning 95 per cent of his first-serve points (37 out of 39) and committing just eight unforced errors.
Jarry had enjoyed an impressive fortnight in Rome, defeating Stefanos Tsitsipas and Tommy Paul on the way to becoming the first Masters finalist from Chile since Fernando Gonzalez (also at the Italian Open) in 2007.
However, just two break points were enough to deny the 21st seed a fourth career ATP title, with Zverev eventually converting his fourth championship point to ensure a return to the winner's circle.
Data debrief
Zverev joins Rafael Nadal (10) and Novak Djokovic (six) as one of only three players since 2000 to win the Italian Open on multiple occasions.
Landing his second crown in Rome seven years after his first, it marks the longest gap in seasons between two men's singles titles at the event in the Open Era.
Meanwhile, Zverev became the most successful German male in ATP Masters events since the format's introduction in 1990, with his sixth such success seeing him eclipse Boris Becker's total of five.
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