Djokovic is very apologetic after getting the most fortunate of flicks off the tape. The ball flops over just an inch on to Thiem's side of the court.

Still, Thiem, helped by more first serves, wraps up the game quickly.

Tim Henman
Former British number one on BBC One

Djokovic's mental resilience is going to be key now. The times this week when the going has got tough he hasn't looked that engaged.

Image source, Reuters

You didn't expect the great man to panic did you?

The Serb holds to love.

There was nothing in that set for the vast majority. You don't see Djokovic beaten in the really crucial moments very often.

The Serb gets us under way in the second. He doesn't look flustered and races to a 40-0 lead.

Dominic Thiem wraps up the set with relative ease as the serve finds its mark again.

Djokovic is going to have to do this the hard way. Thiem is a set away from the final.

Image source, PA Media

So, how is your nerve Domi?

The first signs are good - a bruising first serve - but then he misses a backhand.

A point later Djokovic fails with a return and afterwards shapes as if he's going to smash his racquet into submission.

Set point Thiem.

Thiem breaks!

It's a long point and so often you'd expect Djokovic to win those but the Austrian wins it. Thiem gets the ball down near his opponents' toes and Djokovic can't get it back in play.

You'd expect a roar from the crowd at this point but it's just a understated clench of the fist from the 27-year-old.

Thiem finds a powerful forehand winner!

Break point to the Austrian.

Djokovic is the more consistent player at the moment but when Thiem whacks it he really gets some power on the ball.

His latest backhand would have knocked the racquet out of the hands of most players.

30-30. Big point.

Tim Henman
Former British number one on BBC One

The quality is going up as we are getting to the business end of this set. Djokovic is hitting the ball a little bit harder and little bit closer to the lines.

Djokovic lets Thiem off the hook by missing a relatively straight forward forehand.

On we go.

Andrew Castle
BBC Sport tennis commentator at the O2 Arena

I think that Thiem's forehand is not as good as he is going to need today. The pressure is on him.

Thiem is ticking. Another forehand error - those are starting to come too often - and another yelp of frustration. There's a grumpy look to his box too.

Deuce.

Image source, Getty Images

The point of the match so far!

Djokovic turns defence into attack brilliantly and looks certain to win it at the net.

Thiem has other ideas. He lands a sensational lob a smidge inside the baseline.

Even Djokovic is applauding.

40-30.

An Austrian cry echoes around the O2 after Thiem misses a forehand.

30-15.

Now then, Dominic Thiem serving to stay in the set...

A crunching ace to start. 15-0.

I'm bashing away at this live text while my girlfriend makes a cake behind me in our kitchen. The joys of lockdown 2.0.

Thiem shakes his head after pushing the ball wide having stepped into a forehand. We still haven't had a break point in the match. Djokovic holds serve again.

Dominic Thiem really does get some impressive top spin on the ball. It's Nadal-esque. A forehand looks like it is going way long before dropping inside the lines.

It's a nice time for a love-hold. Thiem does just that and levels up again at 4-4.

Thiem is annoyed after a deep forehand is called out. He can't argue. As I mentioned in the previous game, all calls are being made by the automatic Hawkeye technology so there are no challenges.

Djokovic plays a tricky volley from down near his toes with perfection. He's out of that tricky spot like Indiana Jones in The Last Crusade.

Image source, Reuters

Now it's Thiem's chance to apply the pressure.

Djokovic is at 0-30 on his own serve after punting a poor forehand wide into the tramlines.