GAME, SET AND MATCH! - ZVEREV 6-4 3-6 6-4 CILIC. What a turnaround. Zverev comes out all guns blazing, firing a pair of supreme winners to tee up triple match point. The young German doesn't let up there, sealing it on the first with a thumping put-away at the net to cap his debut here with a victory in two hours and five minutes. It was a real rollercoaster but at the end of it all, he joins Federer at the top of Boris Becker group after the first of the round-robin matches.
Alexander Zverev - Marin Cilic
ATP World Tour Finals - 12 November 2017
World Tour Finals – Follow the Tennis match between Alexander Zverev and Marin Cilic live with Eurosport. The match starts at 21:00 on 12 November 2017. Our live coverage lets you follow all the key moments as they happen.
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ZVEREV 6-4 3-6 5-4 CILIC. That's a welcome love hold at such a big juncture in this contest. Zverev playing with real authority there. Cilic must hold now to stay in the match.
ZVEREV 6-4 3-6 4-4 CILIC. Good response from Marin. The trusty serve plays its part as he levels up at the business end of the match. Whoever blinks now will surely lose.
ZVEREV 6-4 3-6 4-3 CILIC. Zverev has found an extra gear at a crucial moment in the match. He blitzes through a love hold. Pressure on Cilic now. He's been the better player for most of the match, but we saw what happened when Zverev had a purple patch at the start of the opening set.
BREAK! - ZVEREV 6-4 3-6 3-3 CILIC. Wow, has the momentum swung back to Zverev? At 40-15 down he hurls his racket to the floor. It's usually a bad sign, but it seems to inspire him. He corks a backhand winner down the line of the next point and then plays some scintillating tennis at the net to make deuce and storm through to break back.
ZVEREV 6-4 3-6 2-3 CILIC. Great fight and spirit from Sascha. At 0-30 it looks bleak, but he keeps his fading hopes alive to battle through a hold from deuce.
ZVEREV 6-4 3-6 1-3 CILIC. Marvellous from Marin. The Croatian consolidates, producing some magic hands at the net to provide a block volley winner after Zverev had threatened to force deuce from 40-0 down.
BREAK! - ZVEREV 6-4 3-6 1-2 CILIC. Cilic unleashes a stonking crosscourt forehand pass to make 30-30 and is then gifted the break courtesy of two untimely errors from Zverez. Both players have gone for it at the start of this set, but it's the Croatian who has delivered.
ZVEREV 6-4 3-6 1-1 CILIC. Excellent back up play to make the most of that big serve. Cilic remains unfazed by Zverev's vibrant start to set 3 and eases to a hold to 15 to move level. It's developed into a very watch-able showdown.
ZVEREV 6-4 3-6 1-0 CILIC. Zverev comes out fired up and starts the decider in positive fashion. Cue some fist pumps and a bit of psychology. Will it affect Cilic? Probably not. He just needs to keep doing what he's done for the past set and a half.
SET! - ZVEREV 6-4 3-6 CILIC. It's all square! Cilic holds his nerve, fighting back from 15-30 to deservedly serve out a set in which he was the much more consistent and attack-minded player. Zverev has leaked far too many errors since his barnstorming start to the match. The smart money would be on Cilic right now, but don't rule out another purple patch from the German youngster.
ZVEREV 6-4 3-5 CILIC. Sascha working hard just to keep this set alive. He ventures into the net to despatch an overhead to save set point before a couple of solid serves help him over the line. Cilic to serve for it next.
ZVEREV 6-4 2-5 CILIC. The pattern continues. Zverev pushed on serve while Cilic breezes through his, this time with another love hold. He's one away from levelling the match.
ZVEREV 6-4 2-4 CILIC. Zverev refuses to cave as Cilic presses for what would surely be a set-clinching double break. The Croatian can't quite conjure up the BP as he overcooks to the baseline to let Sascha off the hook from deuce.
ZVEREV 6-4 1-4 CILIC. This is looking all set for a decider. Cilic surges to a love hold, finishing with an ace as Zverez continues to toil.
ZVEREV 6-4 1-3 CILIC. A corker of a crosscourt winner off that vicious two-handed backhand claims a solid hold to 15 to stop the rot and get Zverev on the board.
ZVEREV 6-4 0-3 CILIC. More unforced errors of the forehand for Zverev prove costly once more. He blows a decent opening at 30-30 and Cilic wastes little time sealing the game on the next point to consolidate.
BREAK! - ZVEREV 6-4 0-2 CILIC. A fist pump and a cry of delight from Marin as a Zverev miscue flies way long. It comes on a third BP after the4 German had dug deep to save two and make deuce. The pendulum swings the way of the Croatian.
ZVEREV 6-4 0-1 CILIC. This time Cilic makes sure there's no early blip. He holds to 30 to take the early initiative and the scoreboard advantage at the start of Set 2.
SET! - ZVEREV 6-4 CILIC. Super stuff from Sascha. He serve it out to love to take the opener in 43 minutes.
ZVEREV 5-4 CILIC. Marin poses the serve-out question to the German as he rattles through another love hold. How he must rue that shocker in the opening service game. Over to Zverev now - how's his nerve?
ZVEREV 5-3 CILIC. Deja vu for Zverev as a commanding 40-0 lead courtesy of some big serving and a sizzling crosscourt backhand winner begins to erode away. Cilic gets to 40-30, but a timely ace down the middle T moves Zverev to within one game of the set.
ZVEREV 4-3 CILIC. The momentum is with Cilic as he claims another simple and highly effective hold to love - but he's still down on the scoreboard. Is that break back coming or can Zverev lift himself to get over the line?
ZVEREV 4-2 CILIC. Zverev threatens to beat himself as 40-0 slips to deuce with a trio of errors into the net. It's a mixed bag from the world No.3 as he struggles to get it done from deuce. Cilic grows into the game but blows a big, big chance on the forehand to earn a break opportunity. Zverev responds and comes through another tough hold.
ZVEREV 3-2 CILIC. Cilic finally finds some rhythm on serve and puts some easy points together. He holds to love with the minimum of fuss.
ZVEREV 3-1 CILIC. Zverev hurls down an ace to fend off BP after a pair of poor forehands into the net had given Cilic hope of parity. The unforced errors are creeping in for Zverev who had started like a juggernaut, but he gets the job done with sizzling forehand winner from deuce to stay in charge.
ZVEREV 2-1 CILIC. Marin needed that. Zverev threatens to force him to deuce and make life difficult once more, but this time the German youngster's radar is just off as he fires long to allow Cilic to get on the board.
ZVEREV 2-0 CILIC. Sascha consolidates to love. The German is clearly loving the stage so far. Cilic has lost five of his previous six matches here and will have a familiar feeling in the pit of his gut right now. He's going to need to move it up a couple of gears if he's to change it.
BREAK! - ZVEREV 1-0 CILIC. The first serve deserts Cilic from the off and it gives Zverev an early chance. The Croatian rediscovers it just in time to stave off break point with a bullet down the middle T and make deuce. The No.5 seed can't pull free though and Zverev outlasts him in two lengthy rallies, securing an immediate breakthrough with a delicious low drop volley.
Time to get underway; Cilic is serving first.
OMEN FOR ZVEREV FANS? Cilic has been beaten by the eventual champion in his previous two opening round-robin matches against Novak Djokovic and Andy Murray (2016).
This is Cilic's third appearance at the end of season tournament. It's Zverev's bow. Will there be first-day nerves from the German?
HEAD-TO-HEAD: Zverev leads the match-up 3-1. In their most recent encounter earlier this year in Madrid, the German starlet came from a set down to make the last 16 with a 6-7 6-3 6-4 triumph. Cilic's only victory came in their first ever showdown in Washington back in 2015.
Earlier today, Roger Federer got his bid for a seventh end of season crown with a 6-4 7-6 victory over Jack Sock in the first match in Boris Becker group.
Hello and welcome to live updates of the second match of the 2017 Nitto ATP World Tour finals. It's rising star and world No.3, Alexander Zverev against 2014 US Open champion, Marin Cilic in Boris Becker group.