"There goes 1987," John McEnroe famously said when his wife Tatum O'Neal announced she was pregnant with the couple's second child.
He might as well have said "there goes the rest of my career" since he would never win another Grand Slam again. Such are the distractions of parenthood.
Is new-dad Novak Djokovic, whose baby boy Stefan was born just over three weeks ago, likely to be similarly put off his stride?
Recent match results would suggest not. At the ATP Masters in Paris he stormed through to overall victory without dropping a set. This week at the ATP World Tour Finals he has impressed with wins over Marin Cilic and Stanislas Wawrinka, the scores a convincing 6-1, 6-1, followed by 6-3, 6-0.
Perhaps he's basking in a warm post-natal glow. Perhaps he's just very good at blocking out distractions. Maybe he's simply decided not to let a newborn change his life.
When you earn over £20 million a year, it's easy to sidestep normal paternal duties. You don't think Novak is going to be changing nappies, do you? Heating up milk bottles? Burping little Stefan at 3 in the morning?
You must be Djoking. Even his wife Jelena is sure to employ the best hired help on the tour.
Modern ATP couples delegate whatever they can. Novak is used to employing a coach, a manager, a fitness trainer, a physio, a personal assistant, a driver, a racket stringer, a man to peel his blessed bananas. With this lot on the payroll, he’s hardly going to volunteer to get his hands dirty with baby effluent.
Come on! Be realistic. He'll employ a whole army of nannies if he has to. He'll rent out a second five-star hotel room with extra soundproofing to ensure his precious sleep is undisturbed.
Like Victorian babies of a certain class, Stefan will be fed, burped, washed and regaled with the latest adventures of Peppa Pig before finally being presented to his father at bedtime.
Novak is, after all, a stickler for order and routine. This is a man who checks his hydration levels every morning by observing the colour of his pee, and who follows a strict gluten-free diet.
We mortals like to think out celebrities are normal parents like us, juggling careers and parental responsibilities. Partly because we want to imagine them under the same pressures, and partly out of some romantic notion of parenthood.
But our celebrities live in another universe – one where the very best professional help can be hired, whatever the duty.
Yes, Novak may end up dealing with a handful of Stefan's nappies, and feeding him the odd bottle of milk, but it will be for novelty value rather than out of a sense of duty.
If Novak chooses to concentrate on his tennis, his newborn will have virtually no affect on his tennis schedule at all.
To reassure himself of this, he simply has to look at recent tennis history. Since 1990, a total of nine dads have won Grand Slams: Wawrinka, Federer, Agassi, Costa, Kafelnikov, Korda, Becker, Gomez and Lendl.
And you can bet they all employed excellent nannies.
Will Daddy Novak win the next Grand Slam – the 2015 Australian Open? Unibet has him as favourite at 2.40, followed by Rafa Nadal at 5.00, Roger Federer at 6.00 and Andy Murray at 6.50