Federer and Djokovic are the favourites to win the season-ending tournament at the O2 Arena in London.
The pair met in the Paris Masters semi-finals last week, which Djokovic won, but have been kept apart in the group stages of the Finals.
Cilic has seen a recent upsurge in form and Sky Sports pundit Annabel Croft reckons he could cause an upset.
The Croatian has been drawn in the same group as Djokovic, Alexander Zverev and John Isner.
“I think all of us have been really impressed with Marin Cilic,” Croft told Sky Sports.
“He had a little bit of a dodgy couple of months leading towards the back end of this year.
“But he is suddenly starting to find his form again and is fresh.
“The way he pushed Novak Djokovic [in the Paris Masters quarter-finals] and the tennis that he played.
“He loves the indoors, he is moving exceptionally well. He is playing aggressive.
“He is serving exceptionally well so I would say he is going to have a very good O2.
“I just feel it is a little bit different this year. It is not wide open, Novak is the obvious favourite, but the others are fighting for the position behind that.”
Meanwhile, fellow pundit Greg Rusedski believes Djokovic will win the tournament, although he has tipped Federer to push him close.
“I would say Federer. If Federer plays like he did against Novak Djokovic and says ‘Ok, I feel good now, I am relaxing’ he has got a shot,” Rusedski added.
“Also the court are a little bit quicker and the ball slides through more.
“But we have got to see a consistent Federer and that was by far his best match in a long while.
“Don’t write out Roger Federer because he is desperate to win another title this year.”
Source : EXPRESS