Alexander Zverev and Jack Sock will play in crunch match in Boris Becker Group on Thursday

Jamie Delgado and Greg Rusedski are torn between who they think will come out on top of the winner-takes-all encounter between Alexander Zverev and Jack Sock at the ATP Finals on Thursday night – live only on Sky Sports.

With one win and one loss at The O2, Zverev could still feature in the other half of the draw to Federer in Saturday’s semi-finals should he prevail in the meeting with Sock.

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Sock kept his dreams of a fairy-tale finish to his season alive, overcoming a 4am fire alarm to beat Wimbledon finalist Marin Cilic, and becoming the first American to win at the elite season-ending event since Andy Roddick in 2007.

“This is a huge, huge match for both,” said Andy Murray’s coach, Delgado. “Sock’s been really impressive in this tournament so far. His movement against Marin Cilic was incredible and he showed unbelievable defence. We all know him for a big serve and a big forehand, but actually his backhand made the difference in his last match.

“His confidence is sky high because he has just won Paris, but I’m a bit torn between who will win. I’ve gone with Zverev so I’ll stick with that prediction, but it will be a close one.”

Here's the best of the action from Zverev's three set defeat to Roger Federer

Delgado felt young German prodigy Zverev played exceptionally well in defeat against Federer and has the potential to set up a rematch with the Swiss superstar in Sunday’s final.

“I thought his performance was great,” added Delgado. “He’s already No 3 in the world and quite possibly a future world No 1 but he’s performed well considering this is his first time here. The belief in himself is great.

“There will be pressure on Zverev to come through, but it’s going to be a very, very close match.”

Rusedski predicted a win for 25-year-old Sock before the tournament believing that he has the momentum heading into London, but says it’s all about whether Zverev will show up on the night.

“I predicted Sock in three sets and although there will be more pressure on Zverev to win, he’s a little more complete but they’re very much opposite in the respect that Zverev’s backhand is one of the best of the game while Sock is always searching for his forehand,” said the former US Open finalist.

“If we see the Zverev that showed up against Federer in that first set, that was absolutely brilliant, then it’s quite a toss-up.”

Jamie Delgado and Greg Rusedski were speaking to Sky Sports’ Raz Mirza at The O2.

The season-ending extravaganza ATP Finals ends another memorable year which will be covered via our website with live blogs, reports, reaction and expert analysis as the season reaches its climax.

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