Andy Murray says he has no idea how long he will be able to continue playing at the highest level after making a winning return against James Duckworth in the Brisbane International.
The three-time grand slam champion played just 12 matches in the 2018 season after undergoing hip surgery at the start of the year.
Murray got 2019 under way with a 6-3 6-4 victory over Australian wildcard Duckworth on New Year's Day and the Brit plans to savour his time on court, as he is uncertain over what the future holds.
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"I felt like I moved quite well towards the end, which allowed me to get the break in the second set. I think for the first match of the new year after quite a long break, it was alright." the 31-year-old said.
"It's not easy to sum up in one sentence or one answer, it's been a really hard 18 months, a lot of ups and downs, it was tricky just to get back on the court competing again, so I'm happy I'm back out here again.
"I want to try and enjoy playing tennis as much as I can, I don't know how long it's going to last, but we'll see."
The former world number one - who will face fourth seed Daniil Medvedev in the second round - added that it has been tough to see his long-time rivals Rafael Nadal, Roger Federer and Novak Djokovic thriving during his lengthy absence.
"It kills me that I've not been able to be there competing. Obviously the top three spots in the rankings are taken up by the same guys. There is going to come a time where the youngsters take over, but it's amazing what the three of those guys are still doing." Murray said.
"It's not going to go on forever, so me, as a tennis fan, and I'm sure everyone else, just wants to enjoy these last few years while they're still playing. There have been some incredible matches, they are all great champions and brilliant ambassadors for the sport.
"I've been lucky to compete amongst them and hopefully I'll get a few chances in the coming months to play against them again."