It was while Novak Djokovic was waiting to walk on to Centre Court that his opponent, the Russian qualifier Roman Safiullin, surveyed the Wimbledon board of winners to their left-hand side.‘Your name’s everywhere,’ Safiullin said to Djokovic, the elder statesman smiling as if embarrassed and replying: ‘Yeah, I’ve been around a few years… a few decades.’Indeed, Djokovic is the greatest of the game fighting against that dastardly Father Time, and there were worrying times here on Centre when this seven-time SW19 champion looked it.He looked creaky. He looked bothered. He looked like a 39-year-old whose engine was stuttering in the drive for Grand Slam No 25 as he grunted, grimaced and gave up on the odd ball which he might have reached once upon a time.It was in spite of that occasional stiffness that the Serbian won to leave yet more footsteps in Wimbledon history. By beating Safiullin, Djokovic confirmed his 106th match win on the lush lawns of SW19, securing him sole ownership of the men’s all-time record, one more than Roger Federer.Djokovic had never lost a Grand Slam match to a player ranked as low as Safiullin – currently 132nd in the world – nor had he ever been beaten by a qualifier. Those records remain intact, though Safiullin proved an aggressive protagonist on the other side of the net amid this 7-6, 6-3, 3-6, 6-3 victory in three-and-a-half hours which sent Djokovic into Wimbledon’s quarter-finals. Novak Djokovic beat Russian qualifier Roman Safiullin in four sets to reach the quarter-finals Djokovic did show his vulnerability in a hotly contested clash but made it through in the endIt was in the first set, which took 62 minutes to complete via a tiebreak, where Djokovic initially showed his physical struggles and then his psychological strength in this fourth-round victory.Safiullin was leading 5-2, Djokovic was serving, and the 24-time Grand Slam champion seemed distracted. It was sticky on Centre Court, and almost as if there had been an invasion of butterflies with fans flapping in faces. There was some blinding from the sun, a light breeze, and the position of a camera which Djokovic was not having, but nothing that Safiullin did not also have to handle.A few inside Centre Court wondered whether Djokovic might simply sacrifice this first set, and save his energy to start from scratch in the second, as we have seen happen before. The legs appeared heavy and the shoulders slumped. Centre Court tried to encourage their ageing champion with chants of ‘Novak, Novak’ led by a small group of Serbians sitting low in the stands, opposite a chap presumably melting in a strawberry costume on the other side.Djokovic saved two set points for Safiullin and, rather than surrendering 6-2, fought his way to 6-6. At the tiebreak, Djokovic searched for quick kills, including the odd serve-and-volley which did not go his way. He eventually prevailed before exiting Centre Court a set to the good, leaving Safiullin to stew a little on how he was losing despite playing so well.While leading by two sets, Djokovic’s 11-year-old son, Stefan, started playing a game of cards with a friend in the family box. He had seen his old man in this position too many times. He figured it was over, with Safiullin requesting his physio on court to help him with a hip problem.However, Safiullin is a scrapper and crisp on the grass. When he broke Djokovic to take a 4-2 lead in the third set, the Serbian smashed a ball in anger, despite having already received a warning for yelling something untoward in his native language. Unlike when leading 5-2 earlier in this match, Safiullin saw this one through, forcing Djokovic into a fourth set which he could have done without. Despite his underdog status, Safiullin scrapped and made Djokovic work hard for his victoryDjokovic himself has conceded that, at 39 years old, it is a challenge for his body to cope with longer contests. Not only during them, but in his recovery afterwards.That is why efficiency has been at the forefront of Djokovic’s mind over his first week at SW19, and this fourth set was more to his liking, secured 6-3 via a delightfully delicate volley.’I don’t get to feel inferior from the back of the court too often,’ Djokovic conceded as he addressed Centre Court. ‘This was one of those days I didn’t want to stay in the rallies.’Djokovic survived what Safiullin threw at him, however, and will meet either Felix Auger-Aliassime or Alejandro Davidovich next in what will be his 17th Wimbledon quarter-final appearance. If the body holds up, a 25th Grand Slam singles title could yet follow.