Alexander Zverev fends off Marin Cilic to seal opening ATP Finals victory

Alexander Zverev overcame an early wobble to begin his ATP Finals campaign with a 7-6 (5), 7-6 (1) win over fifth seed Marin Cilic.

The 21-year-old, viewed by some as a potential successor to the Big Four who have dominated men’s tennis for the last decade, was far from consistent enough to suggest he could pose a serious challenge to Novak Djokovic this week but at his best was a cut above Cilic.

The third seeded Zverev, who so far in his fledgling career has struggled to translate his obvious talent into prolonged success on the biggest stage, cut a frustrated figure as his service game fell apart early in the first set,

But it was easy to sympathise with the 21-year-old when he saw a 141mph serve fly back over the net and into a dangerous spot as Cilic wrestled early control of the match.

Having fallen 0-3 down early on in proceedings the German let his racket fall to the floor before the change of ends, with grimaces and glances to the heavens the order of the day from Zverev.

Not until the eighth game did the world No.5 really click, a hold to love setting the stage for an impressive break-back as Cilic struggled to get a read on his opponent’s ground strokes.

Momentum was on Zverev’s side as he reached the tiebreaker and, though he would need three set points to claim it, a supreme backhand pass secured the first set.

Zverev was unable to capitalise on Cilic’s leaden-footed start to the second but was unquestionably producing the better shots, typified by a fine backhand along the line in the sixth game.

Having been playing by far the better tennis the German suddenly contrived to hand a break to his opponent with a string of clunky shots the very next game - only to then follow that by immediately breaking back.

Still Zverev did not cool down, fuming at the chair umpire after Cilic was allowed to belatedly, and incorrectly, challenge his serve.

That indignation seemed to fuel the youngster towards a match point secured with an explosive cross-court forehand return. Cilic denied him then but could not in the next tiebreak as Zverev’s class shone through at the decisive moment as he found the lines with his groundstrokes.