Novak Djokovic survived a scare to reach the second round of Wimbledon after battling past Alexandre Muller.
But ATP number six Djokovic also battled a fitness issue throughout the match, having twice called for the doctor in the third set.
A seven-time champion at Wimbledon, Djokovic finally secured a 6-1, 6-7(7-9), 6-2, 6-2 win after three hours and 20 minutes.
Andy Roddick thinks Djokovic will reach the Wimbledon final, with Dan Evans now awaiting the Serbian in round two.
Home favourite Evans progressed into the second round after defeating fellow Briton Jay Clarke 6-1, 7-5, 6-2.
Novak Djokovic shares the fitness issue he had in his Wimbledon win vs Alexandre Muller
Djokovic will now turn his focus to his next opponent, although he was on hand to share insight into his latest struggles during his on-court interview.
The former world number one said: “It’s great to finish tonight before the curfew. I want to thank everyone for staying this late.
“Thank you for the support, it was an amazing atmosphere especially after the roof was closed and thanks for deciding to spend an evening with us, I hope you enjoyed.
“It’s great to be back at Wimbledon, I have to say that first and acknowledge the sacredness of this court and this tournament.
“It has always meant a lot to me and many other players. It is a childhood dream tournament and I never take stepping out at this tournament for granted and enjoy myself, obviously a bit less in the second set.
“But to be quite frank I went from feeling my absolute best for a set and a half to my absolute worse for 45 minutes. Whether it was a stomach bug, I don’t know what it is. I struggled with that.
“The energy kind of kicked back after some doctor’s miracle pills and I managed to finish the match on a good note.”
Novak Djokovic says if he was worried he may have to retire in Wimbledon round one
Djokovic has enjoyed stunning success at Wimbledon over the years, with only Roger Federer boasting more titles.
The Swiss icon has eight Wimbledon titles to his name, followed by the seven of Djokovic, Pete Sampras and William Renshaw.
And Djokovic has come agonisingly close to matching his former rival, only to lose the last two Wimbledon finals to Carlos Alcaraz.
But like the Spaniard this year, the Serbian is now safely into round two, having also discussed whether he was worried about a potential retirement during his opening match.
“No, I wasn’t thinking about that or taking that as an option but I knew something was off with the stomach,” said Djokovic. “Hopefully when that calms down the energy will come back. That is what happened.
“Credit to Alex for playing some really good tennis. He fought in the second set and deserves a round of applause for the battle.
“I think when I faced some break points in the fourth I came up with some good serves and I think overall I served very well today.
“That is one of the things I have been working on and to get as many free points on the first serve as we can.
“Grass is the fastest surface we have in sport, so when you get a lot of free points off the serve and high percentage of first serves in it makes your life a lot easier.
“I think at the start of the third and fourth set that was the case and it put pressure on his service games and I found the right shot and the right time so overall a lot of positives to take from today and into the next round.”
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