Apparently, Federer has spoken in three different languages on court so far today.

Show off.

He's muttering in English (I think) as a line call goes against him. Nae bother, though. He holds anyway.

Gigi Salmon
Radio 5 live sports extra commentator at Melbourne Park

There might not be loads of points won like that, but it's one to take away from this for Struff.

Two break points for Roger Federer, as the second seed starts to make headway in this second set.

Struff fends one off as he stands tall at the net to volley over.

And then comes the most ridiculous 23-shot rally. It's like a game of table tennis at the net and Struff celebrates wildly as he takes the point.

Deuce.

Struff goes on to hold. A terrific hold, too.

Bang!

A blistering forehand winner makes the crowd sing: "Let's go Roger, let's go."

The Swiss, at 40-30, finds a fifth ace to hold.

It's easy to fall into the trap of a Roger Federer love-in, because he is just brilliant to watch.

But credit where credit is due, Jan-Lennard Struff is doing a really decent job. He's got an excellent volley on him and he's using it well here.

Another hold for the German, and he drops just one point on the way.

It's all over for Stan Wawrinka at the Australian Open.

The semi-fit former champion has bowed out against the wonderfully-named Tennys Sandgren, of Tennessee, who dropped only seven games in his 6-2 6-1 6-4 victory.

Image source, EPA

Third time lucky!

Federer serves out the set with a huge ace.

That took 32 minutes. Speedy.

Federer completely wrong-foots Struff on the opening point. The German got his direction all wrong.

Struff tries to challenge another Federer serve and he's wrong again.

The defending champion brings up a solitary set point and it's taken away from after some fantastic hits from Struff.

Deuce.

Federer takes the advantage for a second set point and that goes amiss too when he scoops long.

Back to deuce we go.

Mark Woodforde
Australian 12-time Grand Slam doubles champion on BBC Radio 5 live sports extra

Roger makes it look so easy and majestic, and it's not. He's the best I've seen, without a doubt. He is such a joy.

The gasps turn to ahhhhhs as Federer swipes a backhand with some style to give another body blow to his opponent.

Struff responds with an ace before Roger fights back with a forehand winner.

The German lands another big ace to hold. Federer to serve for the first set and we're only 26 minutes in.

There was literally a gasp from the crowd in the Rod Laver Arena as Roger Federer double faults.

Do they know he is human?

The Swiss recovers with an ace for 40-30, which Struff incorrectly challenges.

Federer holds as the German sends long. Now Struff has to stay in the set.

It's all going horribly wrong for former Australian Open winner Stan Wawrinka.

He's serving to stay in the match against Tennys Sandgren. The Swiss has just returned from knee surgery and looks pretty uncomfortable out there.

Image source, Reuters

Struff comes storming into the net for a bit of volley action. Federer tries to fend him off with a backhand but he almost decapitates his opponent in the process.

The big German keeps his head and also holds to love.

Here we go, then. Federer's on the charge already.

He zooms into a 40-0 lead and Struff plants a wild backhand way over the lines. Hold!

Image source, Gett

David Law
Radio 5 live sports extra commentator at Melbourne Park

Jan-Lennard Struff has played about as well as he can, and he's a break down. Federer looks laughably fresh and young. He's 36 years old.

What do you call a load of geese? Is it a gaggle or a flock?

I ask because there are hundreds of the blighters flying over the arena in Melbourne and causing quite the noise.

I think they're geese, anyway.

Are they distracting Jan-Lennard Struff too? He coughs up a break point and Federer nabs it with a cool, straight, crisp forehand.

David Law
Radio 5 live sports extra commentator at Melbourne Park

Struff is having to play the best tennis he can, explosively, to get two holds. It's as though he's got in the fastest car he can find and said 'catch me if you can'.

Roger's a wily old fox, isn't he?

He holds to love in a game which lasts just 59 seconds.

Struff gains a bit confidence after coming out on top in a diagonal rally cross-court.

He then serves out to hold. Break point saved by the world number 55.

Image source, Getty Images

The line judge is making everyone chortle when screaming "OUT" because it sounds like a very high-pitched "OUCH" instead.

Struff is over-thinking this service game a little bit. He's going hard early doors and he's not quite getting his shots right.

Federer earns a break point but he nets a return from a huge serve. Deuce.