Novak Djokovic moves on, to his ninth semi-final in London. Alexander Zverev remains stuck in a personal dilemma, although he might be relieved to be out of ATP Finals as questions about abuse allegations from his former girlfriend Olya Sharypova continue to haunt him. Their show-or-go shootout on day six was a tense and uneven affair, and Djokovic, a five-time champion, prevailed with his deep-rooted gift of riding out serial crises to win 6-3, 7-6 (4) in an hour and 36 minutes. The world No 1 was satisfied with his performance – and in between flurries of ordinary tennis, there were stretches of excellence from both of them. Djokovic, who lost to Zverev in the 2018 final, beat him for the fourth time in six encounters, although a second look at the tape before he plays the world No 3, Dominic Thiem, on Saturday would not be wasted. Almost inevitably, the emphasis later switched from tennis to the rumblings off court. Asked how other players had reacted to him, Zverev said: “They are all fine to me. The relationship between me and the players won’t change. The players know what’s going on. I have said everything that I can. It’s very unfortunate that these kind of false allegations can put such damage and put the attention away from the sport. But it’s the world we live in right now, unfortunately. There is nothing more that I can do.” Djokovic, who has been nominated to return to the ATP player council and is regarded as something of a moral guide in the sport, gave him qualified support. “I have not noticed he has been treated differently in the locker room, but I have not talked to him about that specific case,” he said. “I did tell him I am here if he needs to talk. He’s been handling it well, by the looks of his results. I sincerely wish for him that he overcomes this soon.” As for the tennis, Djokovic said in the immediate aftermath: “I felt great. Early in the first set he had three or four chances but unlike my last match against Daniil [Medvedev], I found the right shots at the right time. He’s a great player, 140mph serves. It was anybody’s game. In the tie-break I read his approach at 4-3 and served out the match.” Djokovic made a near-perfect start, winning nine of the first 10 points as he raced to 3-0 before needing to wipe his brow. Zverev briefly struggled to control his serve until a love hold calmed his twitching right arm. The rallies lengthened and the level rose appreciably although it took Zverev 20 minutes to find a rhythm, a second ace lifting his spirits, as did two break points in the pivotal seventh game. Djokovic’s tennis slipped a little and he had to hold through deuce with a controlled smash for 5-2. Zverev kept the set alive with his third ace before Djokovic, who had lost his earlier certainty, served out nervously after 33 minutes. Zverev, having re-established his credentials behind an improved serve, hit a pair of aces and a double fault to hold at the start of the second set, which lasted twice as long as the first. Djokovic, who had skipped the Paris Masters to be fresh for this tournament, was briefly subdued, his groundstrokes tentative, his feet not so spritely. A third double fault handed Zverev break point in the fourth game, but he could not cash in after an extended deuce battle. Zverev was hitting hard and deep yet was unable to make the most of his opportunities. Consecutive double faults in the fifth game switched pressure to his end; he saved two break points, one with another ace, and held shakily to stay ahead in the serving cycle just short of the hour. They toiled to the tie-break and Djokovic rediscovered his focus – although his relief when Zverev shoved his final shot into the net was evident in his ritual cup-of-love homage to the (empty) arena. Daniil Medvedev made it three wins out of three in the group stages, beating Diego Schartzman 6-3, 6-3 in the final round-robin match. Medvedev, who was already assured of top spot in his group, will face Rafael Nadal in the second semi-final on Saturday evening.