Daniil Medvedev, saving his best tennis for the last stretch of the season, thrashed the world No 1 Novak Djokovic 6-3, 6-3 on the fourth evening of the ATP Tour Finals to reach the semi-finals of the 12th and final London edition of the event. On this form, the lanky Russian might be the defending champion when the event moves to Turin next year. It was a stunning performance from start to finish and Djokovic, a six-times winner here, was blown away after what was shaping as a marathon in the early exchanges. Nearly every service game in the first 40 minutes went through deuce but after the Serb double-faulted three times to surrender the frame, the contest turned into an embarrassing sprint. Medvedev finished with a burst of aces and clean winners and Djokovic was powerless to reply. Pride kept him in the fight, but he could not tame the Medvedev serve. It was all over in an hour and 20 minutes, when the world No 4 slid a routine forehand into empty space. The 2018 champion Alexander Zverev said after a ragged three-set struggle to get past Diego Schwartzman in the afternoon that to win the tournament for a second time: “I have to win every match, simple as that.” But he might feel the backlash when he plays Djokovic in their winner-takes-all match on Friday. And there were moments in his second match of the week when the world No 7 looked as likely to collapse as prevail before holding the Argentinian at bay to win 6-3, 4-6, 6-3. Zverev’s serve ran hot and cold again and Schwartzman, outgunned away from his favourite clay, did well to force a third set. Asked yet again about his former girlfriend’s abuse allegations, Zverev sighed under his face mask, but at least did not consult his media phone for help. He said of the match: “I feel like I played a lot better [than when losing to Medvedev]. But I didn’t practise that much. After Paris I still had an injury. I need to get used to it, and I hope that every match will be better. I hope on Friday will be even better, because that’s what I need against Novak.” Schwartzman, who lost his opening match to Djokovic on Monday, said, “Today I improve a lot. When I was down 3-1 in the second set I hit many winners, started to play my best. He played better than me in important moments, but the serve was the difference today in the third set.”