Andy Murray's latest defeat has him worried.
In stark contrast to his elder statesman Roger Federer and Rafael Nadal, the world No.1 has struggled in the early stages in 2017.
Murray was outplayed 6-3 6-3 by 59th-ranked Croatian Borna Coric at the Madrid Open on Friday, struggling on serve and making 28 unforced errors.
Murray said his third-round loss was disappointing not only because it kept him from advancing in another tournament, but mostly because of his discouraging performance.
"I definitely think I need to be concerned," the top-ranked Murray said. "It's not always the worst thing losing a match, but it's sometimes the manner of how you lose the match."
"I didn't help myself sort of find a way into the match to start playing better ... you're not always going to play your best tennis, but you can still find ways to make it difficult for your opponent, and I didn't do that at all."
It is Murray's fifth loss in a lacklustre season, winning only one tournament and not making it past three claycourt semi-finals.
Murray, Federer and Nadal. Image: Getty
He lost to Albert Ramos-Vinolas in the Monte Carlo third round, after leading 4-0 in the deciding set, then was eliminated by Dominic Thiem in the Barcelona semis.
"Against Thiem ... I was disappointed to lose, but I felt like I competed really well.
"I did some good stuff in the match, found a way to turn it around and make it a tough match for him. Whereas today, I didn't really do any of that stuff. That's concerning. So I need to think about exactly why that is, what I can do about it."
Murray's only title of the year came in Dubai. He expects to play in Rome next week before the French Open, where he lost to Djokovic in last year's final.
Murray entered the clay season after an elbow injury that kept him out of the Miami Open and the Davis Cup quarter-finals.
"That's no reason for how I played the last few weeks. That's not an excuse. However, when you do miss a period of time, getting back into playing matches, the most important thing is to play. I didn't for a month. That set me back a little bit.
"Things can turn around quickly in tennis ... but you need to have the right sort of ideas, correct ideas, understand why you're in the position you're in. Hopefully, I can do that ... and play better in Rome and Roland Garros."
Federer is off to an incredible 19-1 run to start 2017, winning the Australian Open, Indian Wells and Miami Open.
Nadal has won back-to-back titles in Monte Carlo and Barcelona and is the early favourite at Roland Garros.
The stunning resurgence of the tennis legends will have Murray looking over his shoulder, in serious danger of losing his No.1 ranking.
At last count Federer was leading the ATP 'Race to London' (the official rankings system that helps decide who plays in the end-of-year ATP Finals) on 4045 points, just ahead of Nadal on 3735.
Murray is languishing in 11th place, while World No.2 Djokovic is 23rd.