It was a ‘no bet’ day for us on Friday after Stefanos Tsitsipas failed to beat Rafael Nadal, thereby eliminating Daniil Medvedev from the tournament and we move on now to the semi finals on Saturday.

It’s certainly been a trend-busting tournament, with eight underdog winners so far (never been more than five before) and already seven matches that have featured at least one tie break (not since 2009 have there been more than that).

And never in the 10-year history of the Tour Finals at the O2 have their been more than seven matches whose opening sets have gone to more than 10.5 games – but that trend may go as well in 2019’s tournament.

Looking at the service hold numbers of today’s four semi finalists in their three matches at the O2 this week we se that Stefanos Tsitsipas has held 94.7% of the time, Roger Federer 90.8%, Dominic Thiem 85.2% and Alexander Zverev 89.7%.

So, with the opening match of the day being Federer and Tsitsipas at (not before) 14:00 UK time on Saturday the price of around 3.75 on there being a set one tie break looks decent.

Tsitsipas has held almost 95% of the time in matches against opponents that break a lot in Rafa Nadal and Daniil Medvedev (plus an off-colour Zverev) and assuming that the Greek is fit he looks likely to be strong on serve again versus Federer.

This pair clashed only last month on Fed’s home turf of Basel and it was a pretty comfortable win for Federer that day, but Tsitsipas was messing about with his game that week and I expect this match to be tighter.

The conditions look to be a bit quicker here than in Basel and in what was a fairly routine win for Fed that day he only broke Tsitsipas twice.

I said in my preview of Federer against Djokovic the other day that I expected a better performance from the Swiss against the Serb than we’d seen from him in his first two matches and that’s what happened, but can he retain that level today?

I said ahead of that one: “whatever he says Fed will be keen for revenge for that Wimbledon loss to Djokovic,” and his fired-up display showed that to be the case, but Djokovic was surprisingly poor and struggling with an elbow problem, too.

Of his own injury problems, Tsitsipas said after a tough three-setter with Nadal on Friday: “My body feels well currently. I don't feel pain anywhere. I feel fresh, honestly. After having a long, difficult match like this, I feel like I can go out and play tomorrow [Saturday] the same way. So I don't have any problem with that.”

We’ll see how true that statement is come Saturday afternoon, but the way that this pair has been serving this week leads me to take a chance on the set one overs here.

The evening match sees Dominic Thiem take on Alexander Zverev and on the respective levels that this pair have shown over the last few months and the season in general you have to make the Austrian favourite.

Thiem’s also won five of his seven matches against Zverev (including the only one played on indoor hard in Rotterdam in 2017 as underdog), but most (five) of those matches were played on clay.

Thiem clearly took his foot off the gas against Matteo Berrettini having already qualified for the semi finals and that performance should probably be overlooked, but it’s the fluctuating level of Zverev that makes this one tough to bet on.

Zverev was pretty good against Nadal, then poor against Tsitsipas and finally okay again versus a demotivated Medvedev, but once again in that latter match Zverev only won 33% of his second serve points.

And that may well be the difference between this pair on Saturday, with Zverev having struggled all season on second serve (averaging just 44% of second serve points won on all surfaces).

Indeed, this week Zverev has won an average of just 35.6% of his second serve points, while Thiem is way ahead on a healthy 56.3%, which suggests Zverev will have to rely mainly on serve to win this.

Thiem’s first serve has been one of his key improvements lately on hard courts, but he’s only won 67.3% of his first serve points this week at the O2 (Zverev 83.9% of his) so the first serve on Saturday will be a key battleground.

I’d expect Thiem to find a way to win this on current form, with Zverev impossible to rely on still, but 1.68 is too short for me.

Best Bet

0.5 points win over 12.5 games in set one of Tsitsipas/Federer at 3.75