Hello and welcome to LIVE updates of the second semi final at the 2019 Nitto ATP finals. It's Dominic Thiem against defending champion, Alexander Zverev. The players are due on court from 20:00 GMT.

GAME, SET AND MATCH! - THIEM 7-5 6-3 ZVEREV. It's all over! Thiem serves it out to 15 and marches into his first end-of-season final at the expense of last year's champion. The Austrian played the big points better and proved too solid in the end. He gets the job done in one hour and 34 minutes and will now battle Stefanos Tsitsipas for the trophy on Sunday evening.

THIEM 7-5 5-3 ZVEREV. The defending champion poses the serve-out question. Is this his last stand or can he pull off a late, late surge to keep his hopes of back-to-back titles alive? It's a tall order, but anyone can get twitchy looking to serve for the match...

THIEM 7-5 5-2 ZVEREV. Thiem manages to wriggle out of danger after missing a trio of very make-able forehands. He is made to fend off break point and goes on to consolidate from deuce. He's one game away from the final.

BREAK! - THIEM 7-5 4-2 ZVEREV. Sascha gets vocal as he tries to rescues himself... from himself. At 40-15 he suddenly implodes. The second serve syndrome rears its ugly head and he faces three break points. The German staves off two, but Thiem's movement proves decisive as he peppers his opponent with probing shots before striking first blood in Set 2.

THIEM 7-5 3-2 ZVEREV. Thiem has targeted the Zverev forehand to great effect at times. He does it for 40-30 before turning on full power mode from deuce to overwhelm Sascha's defences.

THIEM 7-5 2-2 ZVEREV. The server has had a dominant start in Set 2. No danger again for Zverev as he blitzes his way to a love hold. Great for the training manual, but it's making it tough for the crowd to get truly energised by what they are seeing.

THIEM 7-5 2-1 ZVEREV. Wonderful hands from Thiem. A pick-up drop-shot right at his feet shows sublime touch and is the perfect way to clinch the love hold.

THIEM 7-5 1-1 ZVEREV. Thiem wins a dance off at the net, but it's as good as it gets. Sascha gets a much-needed lift with an easy hold to 15.

THIEM 7-5 1-0 ZVEREV. Too good. Thiem has clearly been buoyed by that finish to the first set, while it's a whole different story at the opposite end of that net. It's a love hold and the Austrian has that scoreboard advantage once more.

Oh dear!

Indeed.

SET! - THIEM 7-5 ZVEREV. And there it is! Thiem has made a habit of playing the big points the best in this tournament and he raises the bar on his return game to snare two set points. The crowd are dismayed when he blows a chance of a forehand winner into the net, but the set is gifted to him on his second chance as Zverev's double fault demons from the season return at the worst possible time.

THIEM 6-5 ZVEREV. Clutch serving from Thiem after Sascha had posed the question by outlasting him in a pulsating rally to make 15-30. The Austrian is guaranteed a shot in the tie break now, but can he find his range and go for broke on his return game right at the death?

THIEM 5-5 ZVEREV. Domi does a decent job of finding his returns, but can't quite apply the heat. Zverev double faults for deuce, but does enough to keep the No.5 seed at bay.

THIEM 5-4 ZVEREV. Are we hurtling towards a tie break? Thiem is raising his level on serve too. A lovely one-two punch seals the deal as he rattles through a highly efficient love hold.