YOU'VE got to hand it to Roger Federer.

Yesterday, he played and tormented Ivo Karlovic the way a stray cat would torment a mouse.

He won 6-3, 7-5, 7-6. No sweat. No worries. Just a regular day at the office.

Yet, in the televised interview which followed, he was smiling as he summed up the match and the season so far.

He made it sound tougher and more trying than it was, tossing pleasantries and compliments at his beaten and broken opponent.

This guy Federer had a future, if he ever wanted it, as a charming Swiss diplomat.

I mean, there he was, with so much lustre that Karlovic had to slip on a pair of sunshades midway into the second set to block out the Federer glare.

But the shades couldn't close the gulf in class. It was apparent. It was Federer and Federer alone.

Before the match, someone mentioned that should the Williams' sisters make the final on Saturday, they will boost their combined bank balance by a hefty £1.275 million ($3.06m) even before the first ball toss is made.

The winner, you see, gets to pocket £850,000.

That statistic settled something later in the night.

We knew why Federer and Karlovic ran so hard under the midday sun. It was that £850,000 carrot. That's why.

Now, you will say, Federer has won US$48m ($69m) so far. Surely that's enough. But it never is. And that's always one of the reasons why he is so intense. Money and greatness, indeed, make an intoxicating mix.

Yes, Federer was relentless on centre court.

The score might have flattered the Croatian. But the fact that it lasted just one hour and 43 minutes said something about the ease of the victory.

Yesterday, we hoped Karlovic would start thinking about money and make a fight of it - if only so that we would see it go beyond three sets. To his credit, he tried. He pushed the second set to 12 games, and the third set to a tiebreak, too.

But when things got a bit rough - like in the fifth game of the third set when the Croatian won to lead 3-2 - Federer was tough and smart. And he had his wits about him. He didn't have to brandish his superiority. He just held it in reserve and squared things up in the very next game - even though he let it go to deuce.

Yes, unlike Federer, the 2.08-metre Croat was never able to bring off the really big points under pressure. That was the difference.

So they gave the Swiss a standing ovation. Nothing unusual. Indeed, come Sunday, we would have no quarrel should he collect that £850,000 winner's cheque.

But first, there's tomorrow's semi-final where Tommy Haas awaits.

The German streetfighter versus the Swiss master.

Haas, at 31, is a veteran on the men's Tour, but he played with the exuberance of youth against Novak Djokovic - a player nine years his junior. His serve was pure tracer fire. His stalking of the baseline was near perfection.

Poor Djokovic. He tried. But over the two hours and 44 minutes - 61 minutes longer than the Federer-Karlovic match - the German was always in charge, winning 7-5, 7-6, 4-6, 6-3 to set up the clash against the man they are already calling the world's greatest player. Surely that will be something to savour.

However, this is my peeve. I think I've seen this movie before - and I swear I know the ending. The Swiss marches on, and on, and on...

But let's wait and see.