Russell Fuller
BBC tennis correspondent at Melbourne Park

How can Roger Federer's eyesight be that good?!

Federer's getting mardy again about challenges.

This time he's held his hand up to dispute a Berdych shot on the baseline. We go to Hawk-Eye and Fed has called is right - it's out by a tiny, tiny margin. How did he see that?! He gives himself a wry smile as a reward, with a cheeky little raise of the eyebrow.

Federer takes the break point and then the game.

Federer makes Berdych roll his eyes as he claws back to 40-30 with a nice return.

Federer plants the ball into his favourite corner - on Berdych's forehand side - to take us to deuce.

Berdych stays calm to take the advantage, but it's snatched away from him by a terrific overhead from the Swiss.

Deuce again.

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

There seems to be a lack of recovery and preciseness from Berdych out in the corners. He was very laboured in that last point.

Federer gets a positive reaction from the crowd as he overawes his opponent for a 40-0 lead.

The biggest cheer is reserved for the final point of the game, which Federer takes with a stretching forehand, flicked into the corner with style.

It's a slightly untidy game from both sides, but Berdych comes through to hold to 15.

Oh, here he is. Berdych is back. He's not visibly limping so we're not sure what the treatment was for.

The snapback goes on and the Czech takes his place to open serve in the third set.

Image source, AFP

Still no sign of Tomas, so Federer gets up out of his seat to do a bit of stretching and lunging.

Just looking at the stats from this match so far.

Roger Federer has hit 43 winners compared to 15 from Berdych, but the Swiss has clocked up 24 unforced errors - 11 more than his opponent.

It's been a strange match, but the defending champion seems more in control now.

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

Berdych has to believe his game is strong and devastating enough to cause some pain on the Federer game plan.

Image source, Reuters

We'll have a break in play as Tomas Berdych has called a trainer.

He's gone into the changing room to get something looked at. We're not sure what just yet.

Meanwhile, Roger Federer stays warm in his chair, decked out in his RF branded gear, looking pensive.

And there we have it.

After 90 minutes, Roger Federer takes the second set, thanks to Berdych hitting long over the baseline.

The pair do battle on the baseline, and Berdych grimaces as he gets down low and mishits a backhand.

A cross-court match-up follows. Federer finishes it with a backhand down the line. Sublime.

Berdych responds by popping the point over at the net, but soon Federer brings up two break points.

The Swiss takes the game by coming into the net and going for the body shot on the backhand, straight down the centre. Boom.

Image source, Getty Images

Yep, Berdych has definitely stepped it up in the last couple of games. He's 15-30 to the good on Federer's serve.

But the Swiss lands a plum forehand past his opponent to level, before an ace on the second serve.

Another ace gives Federer another hold.

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

I've sensed Berdych has tried to re-tool that forehand. When he is seeing the ball big, that forehand is devastating. Under pressure, against the big guys, they direct the ball in to his forehand, and it breaks down.

So far in this tournament and tonight, it seems like he's trying to hit with a bit more trajectory. It's still a vulnerable side for him but it seems to have allowed him to stay in rallies a little longer.

Berdych splays his left hand and attacks the ball with his right as he places a really decent looking forehand winner down court.

It becomes a confident hold to love for the world number 20.

Federer loves to race through his service games but he's not been given the chance to by Berdych.

He still holds, though, thanks to some big serving and delicious trademark forehands.

Image source, AFP

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

It feels ominously close to Federer creating a break of serve. Berdych is hanging in there by a thread.

Image source, Getty Images

Berdych kicks the back of his trainers and takes a deep breath.

Another hold in the bag. Can he get the break?

Tomas Berdych forces Federer's error count up, before clocking the net himself for 30-15.

He finds a big serve to move closer to a hold, before Federer brings out a mid-air forehand winner to pull himself back into the game.

Berdych coughs up his first double fault for deuce.

These are testing times.