Andy Murray at 30: Time running out or plenty more to come?

Andy Murray, who turns 30 on Monday, says he is "not massively into birthdays".

And that may be no bad thing given the difficulty players have found in winning Grand Slams in their thirties.

Only four men have managed to do so this century: Pete Sampras at the US Open of 2002; Andre Agassi, twice in three years, at the Australian Open; Stan Wawrinka at the 2015 French Open and last year's US Open; and Roger Federer, who won his 7th Wimbledon title at the age of 30 and then so memorably walked away with this year's Australian Open at the age of 35.

The incomparable Serena Williams has won 10 in her 30s, but women too have traditionally struggled to make an impact in their fourth decade.

Since the start of tennis' Open Era in 1968, just 10% of Grand Slam titles have been won by players over the age of 30. It is a percentage I think likely to increase over the next couple of years, as Murray's principal rivals remain the other members of the top five, who have triumphed in all bar two of the Grand Slams contested since the French Open of 2005.

And with the exception of Novak Djokovic, who is seven days younger than Murray, Federer, Wawrinka and Rafael Nadal are all further advanced in years.

Murray beat Lleyton Hewitt to win his first ATP title in San Diego in 2006

My sense is that Murray's motivation and desire remain strong - even though he has already won three Grand Slam titles, two Olympic gold medals, the Davis Cup and been world number one, and has a wife and young daughter with whom he would love to spend more time.

With the exception of a bout of shingles and an elbow injury, which have contributed to a 2017 season which is yet to get out of first gear, Murray has been predominantly fit and healthy since undergoing successful keyhole back surgery in September 2013.

The physical nature of his style, and the reliance on exceptional defensive skills which have broken the spirit of so many opponents, will in time take their toll on his body. So while I am not putting money on him to win the 2023 Australian Open at the age of 35, I do think his prospects remain bright for at least the next two years.

Murray himself speaks openly about the prospect of remaining on tour, and thus remaining competitive, for a good few years yet. Although there may be times when his wife and team need to confiscate his racquet and balls and force him to switch off and relax - which may prove easier said than done.

Winning a Grand Slam title will remain incredibly challenging: just witness what Federer is still able to do at 35, and what a threat Nadal proved on hard courts even before there was a sniff of clay in his nostrils.

Wawrinka is likely to remain a major threat in a Slam if, having survived the first week, he hits his straps in the second, and it would be very unwise to rule Djokovic out of the equation even though he has been far from his best for 10 months now.

The 25-30 age group is headed by Milos Raonic, Kei Nishikori, Grigor Dimitrov, David Goffin and two US Open champions in Juan Martin del Potro and Marin Cilic.

Raonic and Del Potro seem most likely to pose a threat to the established order if they can steer clear of injury, but all of the above have had to soak up a lot of punishment from those serial Grand Slam winners over the years.

Which leaves the under-25s, who are an emerging threat. Dominic Thiem looks a French Open champion in the making: the 23-year-old is at a career high ranking of seven after finishing runner-up to Nadal in both Barcelona and Madrid.

France's Lucas Pouille beat Del Potro and Nadal en route to the quarter-finals of both Wimbledon and the US Open last year. Alex Zverev, at 20 and a career high ranking of 17, has won his first three titles in the past eight months.

And then there is Nick Kyrgios, who is yet to present evidence he can keep it together to win seven matches over a two-week Grand Slam, but has been far more consistent this year and beat Djokovic twice in the space of two weeks in Acapulco and Indian Wells.

So the threat to Murray from the next generation should not be underestimated. Thirty is a significant landmark in many people's lives, but the world number one says he expects to be relaxed about it as he spends the day practising at the Foro Italico before this week's Rome Masters.

"I think the last time I was at home on my birthday and around my friends and family was when I was 13 or 14," Murray told BBC Sport.

"I didn't even know what day [of the week] it was until I was told [last week]. Maybe on the day that will be a little bit different.

"A lot of people put huge emphasis on birthdays and I am sure it will be chatted about a lot, but I haven't thought about it too much."