Hello and welcome to LIVE updates of the first semi final at the 2019 Nitto ATP finals. Six-time winner, Roger Federer takes on Greek starlet, Stefanos Tsitsipas in a battle of the generations. The players are due on court at the 02 Arena from 14:00 GMT.

GAME, SET AND MATCH! - FEDERER 3-6 4-6 TSITSIPAS. The debut dream continues for the Greek starlet. Stefanos Tsitsipas ousts six-time champion, Roger Federer courtesy of an impressive straight sets victory in one hour and 36 minutes. The No.6 seed saved two more break points before sealing it with an ace. The 21-year-old went toe-to-toe with the Swiss Maestro and produced some clutch tennis when faced with the adversity of countless break points. He was then clinical when he had his chances and deservedly ran out victorious. He will now meet Alexander Zverev or Dominic Thiem in Sunday's final.

FEDERER 3-6 4-5 TSITSIPAS. 'Come one,' bellows Fed as he slaps down a big serve to get himself out of dodge. Tsitsipas had pressed to deuce with a stonking forehand down the line, but couldn't unearth a match point. He'll now need to summon all of his nerve as he bids to serve this contest out.

FEDERER 3-6 3-5 TSITSIPAS. Stef double faults for 15-30 but then outguns the Swiss via the forehand face-off yet again. Federer lets out an angry cry. It's not surprising really. He's been outplayed in big moments here. The No.6 seed holds and is just one more away from a HUGE victory in his fledgling career.

FEDERER 3-6 3-4 TSITSIPAS. Federer overcomes a mid-game wobble thanks to some loose hitting from Stef, to sneak a hold to 30 and stay in touch.

FEDERER 3-6 2-4 TSITSIPAS. Federer may have had his chances, but Tsitsipas has out-hit the Maestro at times today. He motors to a crisp hold to 15 to consolidate. The Swiss needs to find another gear - and quick - if he wants to keep his hopes of lifting this title once again alive.

BREAK! - FEDERER 3-6 2-3 TSITSIPAS. Federer looks at his wand/racket in surprise once more as unforced error No.20 skews off the forehand to tee up a BP for Stefanos. The Swiss finally saves one but is made to work from a flurry of deuce points before coughing up another with a rushed backhand wide. Tsitsipas has been clinical all afternoon and duly unleashes a stunning forehand to break and wrestle the momentum back his way.

BREAK! - FEDERER 3-6 2-2 TSITSIPAS. If at first you don't succeed... Federer clocks up triple break point but once again he can't make it count. Tsitsipas has advantage from deuce, but the Swiss reels him in again. A sublime backhand slice, drop shot earns the No.3 seed his 10th BP of the match, and he finally converts as Tsitsipas flashes wide. It's met b huge cheers and chants of 'Roger, Roger!'

BREAK! - FEDERER 3-6 1-2 TSITSIPAS. It's a repeat of that loose game that cost Federer so much in the first set. Tsitsipas goes in for the kill and he gets his reward once more. He's been ruthless with his break opportunities. Fed may well look back and think what might have been if he doesn't find a way back from here.

FEDERER 3-6 1-1 TSITSIPAS. The No.6 seed arrows a beautiful 87mph backhand up the line to clinch a solid hold to 15.

FEDERER 3-6 1-0 TSITSIPAS. Federer moves to the service line and it looks like he means business. The Swiss rampages through a super fast hold to get off to a positive start in Set 2.

SET! - FEDERER 3-6 TSITSIPAS. It's Tsitsipas who finally takes it after a wonderfully topsy-turvy game. The Greek fends off two more break points as the two players exchange some quite sublime rallies. The No.6 seed eventually prevails on a seventh set point to take the opener in 46 minutes.

FEDERER 3-5 TSITSIPAS. Routine from Federer as he races through a love hold to pose the serve-out question to Tsitsipas.

FEDERER 2-5 TSITSIPAS. The young pretender plays his get-out-jail free card after somehow digging his way out of a hole from triple break point down. Federer looks dismayed as he fails to make a big chance count. He's 0/4 from BPs in this set and Tsitsipas is now just a game away from taking the opener.

FEDERER 2-4 TSITSIPAS. Federer stays in touch despite a mini wobble from 40-0 up. The Swiss fires a couple of loose drives off each flank to offer Tsitsipas a glimmer of hope, but the No.6 seed can't force deuce as he fizzes just long.