Henrik Stenson has conceded he is running out of time to achieve his goal of winning a major tournament.
The 39-year-old Swede is the oldest player in the top five of golf's world rankings and, unlike the four men ahead of him, does not have a major title to his name, with his best finish coming when he claimed second at The Open in 2013.
Stenson won the Race to Dubai and FedEx Cup titles that same year but comes into 2016 on the back of right knee surgery he underwent after the Nedbank Golf Challenge in December.
Speaking ahead of the Abu Dhabi Golf Championship, Stenson said: "I don't feel old, but the body certainly starts to feel it I guess.
"In my mind I'm still probably somewhere mentally between 15 and 18 and I'll try to stay that way for as long as possible.
"But of course it's normal. Every sport develops and the young players now they are better at an earlier age. You have all the technology and all the help that you can get to become even better, quicker and the competition is tougher.
"I don't think I have forever, that's for sure, to accomplish what I want to do. It has to happen in the next three or four years, I'm pretty certain of that."
On his surgery, Stenson added: "It all went well. The knee looks fine on the inside but obviously it takes some time to recover and it's a fairly quick turnaround.
"I had exactly the same time span between when they operated on my left knee in 2011 and when I teed it up here in 2012 and it feels the same as well.
"It was a challenge to get back to walking back then and it's the same now. Hitting balls is not an issue; just getting back to walking normally and putting it to the test of walking 18 holes five days in a row is going to be the challenge."