Hello and welcome to LIVE updates of the ATP World Tour finals clash between Stan Wawrinka and Marin Cilic at the O2 Arena. Both of these players lost their opening matches in straight sets so it's pretty much a win or bust scenario in their respective bids to make the semi finals. The players are due on court at 8pm GMT.

GAME, SET AND MATCH! - CILIC 6-7 6-7 WAWRINKA. Stan is the man as he does the damage in the TB once more, beating his opponent for the seventh straight time to keep his tour finals hopes alive. It ends 7-3 as he takes it on the first of three match points as Chila dumps a crosscourt attempt into the net. It means Andy Murray must wait until Friday to try and secure a place in the last four when he takes on Wawrinka. Cilic bows out but will now turn his attention to the Davis Cup final.

TB update: 6-3 Stan. Three match points.

TB update: It's 4-2 at the change of ends. Stan unloading a beastly forehand to seize the initiative.

TIE BREAK! - CILIC 6-7 6-6 WAWRINKA. Stan can sense the finish line as he moves 15-30 up thanks to a trademark backhand and a tight forehand into the net from Chila. The Croatian responds but then gives his opponent more hope with only a second double fault to take it to deuce. It's nervy times but he stays focused and draws the error long from Stan and cannons down an ace to take it to the TB.

CILIC 6-7 5-6 WAWRINKA. No room for error now. Stan moves up a gear at 0-15 and piles the pressure back on Cilic. Will he crack or are we heading for a second TB?

CILIC 6-7 5-5 WAWRINKA. Big reaction from Cilic as he moves level once more. The towering Croatian is bamboozled by a lovely lob at 40-15 but regains his composure to take the next point - and he's rather happy about it.

CILIC 6-7 4-5 WAWRINKA. Cilic hurls his racket to the floor in anger at his efforts as Stan moves 30-0 up. It does him no favours as Wawrinka easily concludes the hold to love without doing much. Marin was his own worst enemy there. He needs to get his head right now, a break of his serve next up would be the end of the match.

CILIC 6-7 4-4 WAWRINKA. Aces five and six come in very handy for Marin as he escapes a sticky situation to level from deuce. Stan overcooked a backhand at a big moment in the game. Will he rue it?

CILIC 6-7 3-4 WAWRINKA. Another rapid hold as Stanimal seals it to love.

CILIC 6-7 3-3 WAWRINKA. Solid hold from Cilic. He stays toe to toe with Wawrinka with a quick-fire game to level. Chila is still very much in this while Wawrinka continues to make some inconsistent errors.

CILIC 6-7 2-3 WAWRINKA. A big hold. Wawrinka reprimands himself as he almost undoes his good work. Cilic benefits from the errors to snare double break point but Stan the Man races back to take the game from deuce. Surely the momentum is with him now?

BREAK! - CILIC 6-7 2-2 WAWRINKA. Stan pulls level! A delicious crosscourt forehand is too good for Marin to retrieve and sets up double break point. The Croatian bats one away but gets stung by another thumping forehand on the second after a very tactical rally.

CILIC 6-7 2-1 WAWRINKA. A sublime drop shot and volleyed lob combo proves to be the pick of the points as Stan gets on the board to 15.

CILIC 6-7 2-0 WAWRINKA. Marin comfortably consolidates for the loss of one point. A fine response to going behind but you have to say Stan's level has dipped again after raising himself for the TB.

BREAK! - CILIC 6-7 1-0 WAWRINKA. Cilic pumps his fist in delight as he hits back straight away. Wawrinka should have been on a high but laboured on his first service game of the set - and paid the price. Not even a high shank into the crowd on the first of double break point could dismay Cilic as Stanimal blazed long off the backhand to offer him some hope of a fightback.

SET! - CILIC 6-7 WAWRINKA. Stan finds his best form in the TB as he outlasts Chila in some long exchanges and cannons down some big serves to rack up four set points at 6-2. Cilic saves one with some cool play at the net but a serve and volley combo sees the Swiss over the line 7-3.

TIE BREAK UPDATE: Stan pounds down an ace to lead 4-2 at the change of ends. Cilic firing long and wide in two lengthy exchanges. Could be key.