Alexander Zverev kept his nerve at the key moments to beat Marin Cilic 7-6 (7/5), 7-6 (7/1) at the ATP Finals yesterday, while Roger Federer was upset by Japan’s Kei Nishikori.
In a contest littered with unforced errors at London’s O2 Arena, the 21-year-old third seed Zverev recovered from a break down in each set to establish an early foothold in the Guga Kuerten group.
 Australian Open finalist Cilic came into the match with the dispiriting record of five consecutive defeats against the young German but broke Zverev at the first opportunity and had two break points to establish a 4-0 lead.
 The 30-year-old Croatian, who has a reputation for faltering when under intense pressure, kept his nose in front but was broken as he served for the set at 5-3 and, buoyed by his comeback, Zverev edge the tie-break.
 In the second set, Cilic again drew first blood, breaking Zverev in the seventh game to establish a 4-3 lead but the German responded immediately to level at 4-4.
 Cilic, seeded fifth in London, dug deep to save match point when trailing 4-5 but the set went to another tie-break, which Zverev dominated, winning 7/1 to seal the match.
 There were a total of 78 unforced errors in the contest — with Cilic hitting 46 of those — as both players struggled to adapt to the court conditions.
 “The court is difficult,” said Zverev. “The court is very fast. And it’s very high-bouncing as well. So, it’s more difficult than in other tournaments, so everybody has to kind of find their rhythm in the first match. 
 “But at the end of the day it was a pretty good match. I’m happy to get the win. That’s the most important thing. It’s important — this tournament is big. It is very important to all of us players.”
 Zverev has long been talked about as one of the brightest talents of his generation and will be keen to make a statement in London after again flattering to deceive at Grand Slam level this season.
Federer lost to Kei Nishikori in straight sets in the Lleyton Hewitt group on Sunday, leaving him in grave danger of failing to qualify for the semi-finals for only the second time in his career.
An early exit for the Swiss veteran would deprive the tournament of star power, with world number two Rafael Nadal already missing through injury.
The title is contested by the eight players who have accumulated the most ranking points over the season and is in a round-robin format, with the best four players reaching the knockout semi-finals stage. 
Federer was handed the Sunday night prime time slot for the opening match of his 16th ATP Finals but fluffed his lines in an error-strewn 7-6(4) 6-3 defeat by Kei Nishikori.
After Kevin Anderson had beaten Dominic Thiem in the day’s supporting act, the crowds packed into the O2 Arena and settled in for another Federer masterclass.
What they got instead were 34 unforced errors flying off the Swiss great’s frame as his timing fell apart, and the sight of a tetchy Federer falling out with the umpire.
Having dug in early on to stay with Federer, Nishikori ended up running away with the match to inflict a first straight sets defeat in the ATP Finals round-robin stages on the 20-time Grand Slam champion.
To sum up Federer’s night, he received a warning from umpire Damian Steiner in the 12th game of the opening set when he bashed a ball into the crowd.
“He thought I was angry. I wasn’t. Now I’m angry because I lost,” said Federer, who will face Thiem today in a match he will need to win to revive his hopes of reaching the semi-finals of the event for a 15th time.