It's semi-final time at the Australian Open

It’s hard to see Novak Djokovic being denied his fifth Australian Open, but five-time champion Serena Williams is vulnerable.

Djokovic has a score to settle when he takes on defending champion Stan Wawrinka, after the Swiss sent him packing last year in the quarters in five absorbing sets.

But the Djokovic of today is a vastly more complete player.

He hasn’t lost a set in 15, and has had his serve broken only once, by the 88th-ranked Andrey Kuznetsov in the second round. That was the only game the Russian won in that set, so it made no dent in Djokovic’s march to victory.

But there’s one chink in Djokovic’s armour, his inability to convert break points on a regular basis.

Converting just 16 of 46 in five rounds could prove costly against Wawrinka, where break points will be at a minimum. That translates to Russian roulette tie-breakers, where luck can play a major role.

But everything else is fine in the Djokovic camp, especially the ratio of winners to unforced errors – critical stats. The Serb has cracked 181 winners, and made 104 unforced errors, so he’s well in credit.

And the year-long partnership with coach Boris Becker has proved to be a big bonus, the icing on the cake.

Although Wawrinka was successful in last year’s Open, Djokovic holds a commanding 16-3 lead head-to-head.

In the second semi, Tomas Berdych leads Andy Murray 6-4 head-to-head. They haven’t met since 2013, when Berdych won both their meetings – at the Cincinnati Masters and Madrid Masters – in straight sets.

But Murray is a better player now thanks to his new coach Amelie Mauresmo, while Berdych is coming off a comprehensive straight-sets win over Rafael Nadal, who of course was “off colour”, as is generally the case after every loss.

Illness or injury, take your pick, but it was historic as Berdych had lost their previous 17 meetings.

Serena?

The 18-time Slammer is without peer as the world’s number one, and if she’s on song, nobody can beat her.

But her form was patchy at the Hopman Cup, and hasn’t been consistent in this tournament either, losing opening sets to Elina Svitolina and Garbine Muguruza.

Serena’s poorest stat are her break conversions – 26 of 62 could get her into big trouble against the free-stroking Madison Keys.

This is the first meeting between the Queen and the teen. The 19-year-old Keys is well worth following, she has a wealth of talent as she showed in her three-set win over Venus Williams in the quarters. Breaking Keys’ serve will be difficult for Serena, especially if she keeps up her current poor conversion ratio.

Keys can beat top-seed Serena, but will need to get out of the blocks very quickly.

The same can be said of Ekaterina Makarova in her all-Russian semi clash with two-seed Maria Sharapova, who had a genuine scare in the second round against Alexandra Panova before winning the deciding set 7-5.

But in the other four rounds Sharapova has been cruising, winning 48 games to just 15. Uless Makarova makes inroads very early, Sharapova will make short work of her compatriot.

In the wash-up, it looks like a Novak Djokovic vs Andy Murray men’s final, and a Serena Williams vs Maria Sharapova women’s decider.

The smokey is Madison Keys.