London - Roger Federer trained his sights on next season after a disappointing defeat in the last four at the ATP Finals brought his 2018 campaign to a premature halt.
The 7-5, 7-6 (7/5) loss to Alexander Zverev at London's O2 Arena means Federer must wait until 2019 for a shot at his 100th title -- a year in which he will turn 38.
However the Swiss was positive about his season and excited about returning to the court next year.
The 20-time Grand Slam champion was out of the blocks in sensational style this season, defending his Australian Open title and at the age of 36 becoming the oldest world number one in the 45-year history of the ATP rankings.
"(Pete) Sampras once upon a time said, 'If you win a Slam, it's a good season'," he said.
He started the year with a career-best 17 straight wins, winning in Melbourne and Rotterdam before losing to Juan Martin del Potro in the final at Indian Wells. Two other titles followed, in Stuttgart and Basel.
But there were also major disappointments -- at Wimbledon he lost to Kevin Anderson after leading by two sets and squandering a match point and he departed early from the US Open.
"So I started great. I played super well in Australia again. So obviously I can't wait to go back there in a couple of months. The second half of the season could have been better maybe. I also have high hopes to always do well.
"I'm happy I gave myself opportunities again in that second half of the season. I maybe lost a couple (of) close matches that could have changed things around for me a little bit. I don't know, Paris or Wimbledon, whatever happened.
"I'm here now. So I'm a little bit disappointed there because I believe I was close. Being close makes me believe I can keep going, I can win again. That's uplifting in some ways."- Djokovic challenge -
The problem for Federer is that Novak Djokovic is back as world number one after elbow surgery and a spell of indifferent form and is dominating the men's game again.
Rafael Nadal, despite his current injury woes, will be the hot favourite to win a staggering 12th French Open.
And Zverev is leading the charge from the younger generation, desperate to replace the ageing old guard who are reluctant to be shifted.
Federer holds the record for the most weeks at number one (310) but now third in the world, he appears to have accepted that his days of domination are over.
"I'm very proud that at 37 I'm still so competitive and so happy playing tennis," he said. "As disappointed as I might be about this match, if I take a step back, I'm actually very happy about the season.
"It's been an historic season in some ways. Got back to world number one. For me, that was a huge moment in my life, to be honest, in my career because I never thought I would get there again.
"Here I am having actually a pretty good season physically, as well, won another Slam... so, yes, you can see it as a very, very positive season."