The 31-year-old Briton returns to action at the Brisbane International in Australia after ending his 2018 season following a straight sets defeat to Fernando Verdasco at the Shenzen Open in China in September.
Murray missed the first six months of 2018 after surgery on his right hip. He started his comeback in England on the grass at the Queen's Club tournament in west London and continued it at Eastbourne.
However he pulled out of Wimbledon in July before competing in two events in the United States before the US Open where he lost in the second round to Verdasco.
"I am able to compete at a high level," said Murray after a practice session with Grigor Dimitrov at the Queensland Tennis Centre. "But I have to back it up a few days in a row. That's the challenge.
"I still have some pain in my hip but I'm in a better place than I was a few months ago."
Murray, the first Briton to top the men's rankings since the system was computerised in August 1973, was circuit supremo for 41 weeks between 7 November 2016 and 20 August 2017. He has since plunged to number 256.
While he was nursing his troublesome hip he insisted he was happy he did not give up his rehabilitation.
"You want to go out on your own terms. If I decided to stop six months ago, having not played or gotten back to a level where I can compete again, I would have looked back and regretted that.
"I owed it to myself to give myself the best possible shot to get back to a level I was happy with."
During his pomp, Murray won three Grand Slam titles inlcuding two at Wimbledon as well as the US Open. There were also 14 crowns at Masters events - considered just below the Grand Slams in terms of prestige.
He was runner-up at the Australian Open five times as well as beaten finalist at the 2016 French Open. "There are still things that I want to achieve," Murray added. "Whether I am capable of that I don't really know.
"I would love to win the French Open but because I have been so close so many times, the Australian Open is the one I would pick to win if I could.
"I missed playing here in Australia and I'm going to go out and compete as hard as I can."
Rafael Nadal, who also missed the end of the 2018 season through injury, is scheduled to play in Brisbane. The 32-year-old Spaniard will be top seed.