Federer is set to join the likes of Nadal, Novak Djokovic and Andy Murray – the other members of tennis' 'Big Four' – in representing Team Europe at the O2 Arena in London, but his fitness issues have led to doubts over the extent of his involvement.
On Monday (AEST), fitness coach Pierre Paganini said Federer would make "a last-minute decision" regarding the nature of his participation in the Laver Cup.
Paganini added: "His aim is to play something, though whether it's singles or doubles we'll have to see," and Federer appears to have opted for the latter option.
On Wednesday, Federer told the Swiss press he would only be appearing in doubles at the event, though his partner is yet to be revealed.
"I'm happy and surprised at how good my shots are. But I won't be able to play singles, that was pretty clear beforehand," he told NZZ.
"That's why it was no longer an option to compete at the Swiss Indoors at the end of October. I guess I'll play doubles here on Friday night and that's it."
Nadal, one of just two men's players to have won more grand slam titles than the Swiss maestro (22, also Novak Djokovic with 21) appears the most obvious candidate, with Federer telling SRF: "Maybe I can play doubles with Rafa, that would be an absolute dream."
Asked whether he had any regrets at the end of his career, Federer added: "Of course, there are smaller things, but I can't think of any examples. I see it as an absolute dream career.
"I had a relaxed childhood. If I had been a bit more professional when I was younger, I might have been more successful.
"But then I might have burned out earlier because it would have been too serious for me."
The Swiss great, who has won 20 grand slam singles titles, announced last week that he was to retire from tennis after battling knee injuries.
When revealing the end of his career was imminent, Federer said: "I've worked hard to return to full competitive form. But I also know my body's capacities and limits, and its message to me lately has been clear".