The 19-time Grand Slam champion is a fans’ favourite wherever he goes.
And that would be all the more useful when using the crowd-interactive replacement Hawkeye system.
There is no Hawkeye in place at the Royal Albert Hall where the likes of Marat Safin, Mark Philippoussis and Pat Rafter are all playing.
But tournament chiefs have a fun solution. If a player wants to challenge they can – and it is sent to the crowd.
The chair umpire asks fans to indicate whether they think the decision is right by holding up ‘in’ and ‘out’ cards laid out on their seats.
Rafter was the first to test out the crowd call method this week when he jokingly challenged a let call.
And we reckon the rule would be perfect for charmer Federer, who has grabbed the hearts of fans across the globe.
At 36, Federer is still at the top of the world game having won two Grand Slams in 2017.
Champions Tennis, meanwhile, is the season-ending finale to the ATP Champions Tour with former Grand Slam champions, world No 1s and national icons competing.
Greg Rusedski, Fabrice Santoro and Juan Carlos Ferrero are all in action at the four-day event which kicked off on Thursday.