World number one Andy Murray says he has "work to do this year" after falling "behind" six other players over the course of 2017.
The rankings are calculated over a 12-month period but six of Murray's rivals have accrued more points this year.
"When we start on 1 January, it's back to square one," said the Briton, who is in Indian Wells having won his first title of the year in Dubai last week.
The 29-year-old beat Fernando Verdasco to win the title for the first time.
But a fourth-round defeat by Mischa Zverev at the Australian Open in January means Murray has ground to make up on Roger Federer, Rafael Nadal, Grigor Dimitrov, Jo-Wilfried Tsonga, Dominic Thiem and David Goffin in the 2017 rankings.
He is, however, likely to retain the number one ranking until at least the French Open.
"I felt like I wasn't a bad player just because I lost a match at the Australian Open," he told BBC Sport after a 16-hour flight from Dubai to Los Angeles.
"Australia wasn't my tournament but I took a break after that, chatted to my team about things that I needed to work on, worked on them, and got to Dubai early.
"I played some good stuff where I hadn't played well in the past. So that gave me a bit of a boost coming here, which is also a place where I haven't played my best."
Ready for the challenge
Murray was the runner-up to Nadal at Indian Wells in 2009, but in the past six years has suffered early defeats at the hands of Donald Young, Guillermo Garcia-Lopez and - in last year's third round - Federico Delbonis.
The thin desert air makes the ball fly and jump off the court, and last year played havoc with the Scot's serve. He held back, for fear of missing, and was beaten in the second match he played.
His preparation had also been far from ideal. On the Sunday before an event due to be staged outdoors in 30C desert heat, Murray spent four hours and 54 minutes beating Kei Nishikori in the Davis Cup on an indoor court eight time zones away in Glasgow.
However, this year's warm up in Dubai was much preferable and Murray was enthusiastic when talking about Great Britain's Davis Cup quarter-final in France.
That tie was secured in February when Britain beat Canada 3-2 without their leading player and will be held after the Miami Masters, which follows Indian Wells.
"It will have been a long stretch, but to get matches on clay is a positive thing - and my team are more pro it," Murray said.
"If I'd gone to Canada, it would have been bad news because physically I was not ready. I was struggling a little bit with the illness so it was a good thing I didn't go."
Having overcome shingles, Murray now has the awkward desert conditions to overcome, but has been given a favourable draw in Indian Wells.
While his quarter is far from treacherous, the bottom quarter includes Novak Djokovic, Nadal, Federer, Juan Martin del Potro, Nick Kyrgios and Alex Zverev.