After a pale performance against Daniil Medvedev, Novak Djokovic increased his level in the must-win match against Alexander Zverev. The Serb scored a 6-3, 7-6 victory with a single break in the early stages of the opening set, prevailing in the second to join Rafael Nadal, Daniil Medvedev and Dominic Thiem in the semis.
Djokovic played better behind the second serve in the opener, saving both break points and delivering one break to take it 6-3. They had a similar number of winners and errors, with Novak creating the gap with his initial shot, hitting more than 30% of service winners and building damage in the shortest range up to four strokes.
The Serb held at love with an ace in the opening game and broke at 15 after the German's only double fault. The five-time champion placed a drop shot winner to secure the third game, taking 12 out of 14 points so far and forging a massive advantage after nine minutes.
Alexander painted a backhand winner to get his name on the scoreboard in game four, falling 4-1 behind following another service winner from Djokovic a few minutes later. Finding the range on serve, Zverev held at 15 in game six with a forehand winner, having to find the same level on the return if he wanted to extend the set.
He created two break chances in game seven, denied by two powerful serves from Djokovic, who closed the game with two smash winners that sent him 5-2 ahead. Alexander produced the third comfortable hold in game eight to prolong the action, only for a couple of minutes, though, as Novak landed a backhand down the line winner at 5-3 to secure the opener in 33 minutes.
Novak Djokovic is through to the semi-final at the ATP Finals.
Zverev kicked off the second serve with a service winner, followed by Djokovic's same shot in game two to lock the result at 1-1. The German fired another good serve to wrap up the third game, creating a break chance in the next one but netting a backhand to squander it.
Djokovic held after three deuces and earned two break opportunities a few minutes later. With no room for errors, Alexander erased both with winners from the field, bringing the game home with another forehand winner to remain in front.
The German rattled off the seventh straight solid service game with an ace at 3-3, reaching 30-30 in the next one but having no chances after a forehand winner from Novak, who leveled the score for the fourth time in the second set.
Feeling the ball, the German secured the ninth game with a volley winner, forcing the Serb to serve for staying in the set. Alexander reached deuce with a forehand winner, moving two points away from taking the set before Novak won the next two points to grab the break and extend the action.
Zverev held at love with another booming serve in game 11 and netted an easy backhand a few minutes later to hand the 12th game to Djokovic and set a tie break, the first in their duels. Novak secured two mini-breaks and won the breaker 7-4 to seal the deal and advance into the semi-final.