Roger Federer has warned his rivals that his confidence has returned ahead of the season-ending ATP World Tour Finals.
The Swiss has endured a frustrating season that has seen him collect just one tour title, while his world ranking has slipped to six.
But the 32-year-old appears to be hitting form at the right time as he reached the final of last week's Swiss Indoors Basel and took world number two Novak Djokovic to three sets in the semifinals of the Paris Masters.
He will once again lock horns with Djokovic in his opening encounter at London's O2 Arena on Tuesday—his 10th match in the past two weeks.
And Federer—who has 17 grand slam victories to his name—is in assured mood ahead of a tournament he has won six times.
"It's been a lot of tennis," he said. "I was hoping for that problem to occur so I'm happy it's gone that way.
"I'm happy with my game and the confidence is back. That can carry you really far so that's good. I like this court. It has a great feel to it and usually I play good tennis here."
Federer has been plagued by back injuries this season, and conceded to having doubts in his ability.
He added: "I feel like it's coming together at the right time for me but it has a different feel because it hasn't been as consistent and as good and as solid as it has been in previous years.
"I'm maybe still a little bit unsure about how high is my level of play.
"You wonder if things are going to be how they used to be just going out there and playing tennis. Warming up for one minute like I used to do when I was 20.
"You do so much work to be able to be in decent shape and then still you're not feeling great. It becomes quite frustrating and a little disappointing.
"But I always see the glass half full, I'm a very positive thinker, and every time it was just important for me to exactly understand why did I have the results I had, why did I play the way I did and why am I feeling the way I'm feeling.
"The moment you get a grip on that it's OK.
"Then it's important to be able to move on and have a plan. If you have no plan or you have the wrong plan then it becomes very difficult.
"I don't think I had that this year but as you go along you gain more information and new insights and it became clearer and clearer, which I was happy about."