Roger Federer of Switzerland returns to face Adrian Mannarino from France during their men’s singles match... [+] on the second day at the 2021 Wimbledon Championships in Wimbledon, SW London on June 29, 2021. - - RESTRICTED FOR EDITORIAL USE. (Photo by Adrian DENNIS / AFP). / RESTRICTED FOR EDITORIAL USE. (Photo taken by ADRIAN DENNIS/AFP through Getty Images) AFP via Getty ImagesRoger Federer could have fallen out of Wimbledon unceremoniously at the first round, if his opponent had been healthy enough to play a fifth.Frances Adrian Mannarino sustained a right knee injury late in the fourth set. He was unable to keep his feet on the ground and had to retire from the match just one point into the fifth. No. No. 6 Federer reached the second round after splitting four sets (6-4, 6-7(3) and 3-6), 6-2.In the seventh game, Mannarino lost his feet and his right leg became hyperextended. Federer finally walked over and he laid on the ground for several more minutes. Mannarino was treated and given medication. He served awkwardly, but was eventually broken in the eighth match. After one point, Mannarino retired from the match.Federer stated on court that it was terrible. Federer said it on court. It is a clear example of how one shot can make a difference in a match, season, or career. I wish him well and hope he gets back on the courts soon. He could have won the match at end, obviously. But he was the stronger player. I wish him the best.France's Adrian Mannarino takes on Roger Federer in their men's singles match. This took place at The All England Tennis Club, Wimbledon, SW London on June 29, 2021. - - RESTRICTED FOR EDITORIAL USE. (Photo by Adrian DENNIS / AFP). / RESTRICTED FOR EDITORIAL USE. (Photo taken by ADRIAN DENNIS/AFP through Getty Images. AFP via Getty Images.Federer, an eight-time Wimbledon champion, turns 40 in August. He will play Richard Gasquet and Yuichi Sugita, but will need to play at a higher level to make it deep into the tournament. Mannarino was ranked 41st worldwide, and even though he entered with a record of 0-6 against Federer, Mannarino controlled the match for over an hour after Federer had won the first set. The Swiss appeared lethargic and had trouble with his forehand.Federer stated that Federer was happy to have another chance at a match. I was very dedicated and enjoyed my time out here today. It was great fun right up to the end.With an early break in the fourth, he did start to turn the tides before the Mannarino injury.Federer stated that Federer tried to reduce the number of points. I felt I had found a good groove at the baseline. After I had the break, it was easy to relax a bit.LONDON (ENGLAND) - JUNE 29, 2018: Roger Federer, Switzerland, plays a forehand volley during his Men's Singles... [+] Match against Adrian Mannarino, France, on Day 2 of The Championships – Wimbledon 2021 at All England Lawn Tennis and Croquet Club, London, England, June 29, 2021. Getty Images/Photo by Julian FinneyFederer caused controversy when he pulled out of the fourth match with Matteo Berrettini at The French Open to make it clear that he wanted to be fresh for Wimbledon. In 2020, he had two knee operations and decided not to continue to play on the red clay in Paris.In the second round of Halle's grass court event, which he has won 10 times, he lost to Felix Auger Aliassime (20 years old). Federer missed the press conference after that match because he was trying to avoid any foolish decisions. This was interpreted by some as retirement talk.Federer will be playing at Wimbledon as a seeded tennis player for the 20th consecutive time. He is hoping to win one more match after losing the 2019 final against Novak Djokovic. Djokovic is on Federer's opposite side, but he still has much work to do before he can even consider a deep run.Federer stated that it was an up-and-down match. Federer said that we were wrestling to find out who could enjoy the baseline more.He was more patient than I was, which I found a credit for.