He has graciously declared Rafael Nadal a deserving year-end No.1 but Roger Federer has no plans on gifting his great rival a first-time season-ending crown to celebrate with.
After grand slam triumphs in Paris and New York, and a runner-up showing to Federer in Melbourne, Nadal was formally recognised as tennis's 2017 king at a special presentation on the opening day of the ATP Finals in London.
It's the first time in four years that Nadal has finished the season atop the rankings and now the Spaniard is top seed to finally break through at the eight-man showpiece at the O2 Arena.
With a tour-best seven titles, including an eighth success at Wimbledon, and just four defeats in 54 matches, Federer might himself have reclaimed No.1 status had he played more than 12 events this year.
"Sure, I would have loved to be it but you can't be it with that many tournaments, so it's no problem for me," Federer said, after he launched his bid for a seventh Tour Final trophy with a 6-4 7-6 (7-4) win over American Jack Sock.
"(Nadal) was better throughout the year. He played more tournaments. He was incredibly successful throughout.
"So I don't have any regrets ... he had more gas left in the tank than I did. I couldn't play as much as I've wanted."
But Federer's sportsmanship can only stretch so far, with the 36-year-old biting back at Nadal's claim that he hadn't won a season-ending title because the tour finale was never held on clay.
"I think it's right and fair that it's indoors as well," Federer said when asked if it would be "fair" to play the event on the 10-time French Open winner's favoured surface.
"There is no Masters 1000s on grass. There is one Masters 1000 indoors: Paris. So I feel like indoors also deserves its place.
"Could it be switched up to clay once in a while? Yeah, maybe. Could we have more 1000s on grass? Yeah, we could have that, too.
"Could we have less (tournaments) on clay, more or hard courts? Could we have more on hard courts, less on clay? Yes, it's all debatable.
"It's not the time of the year for clay, so there you have it."
With his comfortable victory over Sock, Federer remains on track to reach the last four of the Tour Finals for the 14th time in his record 15th appearance.
The second seed will play Alexander Zverev and Marin Cilic in his remaining pool matches, with the top two progressing to the semi-finals.
Zverev edged Cilic 6-4 3-6 6-4 in Sunday's night match with Nadal to open his campaign on Monday against Belgian David Goffin.
Dominic Thiem and Grigor Dimitrov will clash in Monday's other match.
