The hairline fracture in his ankle has not healed as well as had been hoped and he must now have an operation to pin the bone together.
If the operation is successful he would, theoretically, be able to carry on but he could face all sorts of ankle problems later on in life. And, if things went really badly, he could even face all sorts of Tommy Smith-style benefit problems.
So he's taken the sensible option and called it a day.
He'll be missed by everyone at Everton as he's easily been the best 'keeper we've had since Big Nev left us. It's just a pity that we never signed him in 1997 when we had the chance really!
He made 100 appearances for the Blues after we signed him in September 2003. And David Moyes rates that transfer as his best ever signing...but, after some of Moyes' transfer dealings, the smartarses out there will probably call that faint praise indeed!
The timing of the news kind of puts the press hyperbole surrounding Rooney's foot into context. The fat kid might miss a couple of World Cup games but Martyn will never play in a competitive match again.
But, at the time of writing, Radio 5 Live has made no mention of the news and the BBC Sport website puts it behind news about Rooney, Gerrard and Ballack all being unfit.
We'll all miss Nigel and I'm sure everyone wishes him well in his future career as a pub landlord, or whatever it is footballers do when they retire these days!