oger Federer’s participation in his farewell event in London this week hangs in the balance amid more injury problems.
The 20-time Grand Slam champion announced last week that he was retiring from the game and that the Laver Cup at the O2 would be his last tournament in the professional ranks.
But hopes of playing are in doubt over the ongoing knee issue, which ultimately led to his retirement announcement.
The 41-year-old is still hopeful he can play a part in the event, which pits Team Europe against Team World from Friday to Sunday, but will make a late decision over his fitness.
There had previously been speculation that Federer might only play in the doubles format of the Laver Cup but a reserve has been called up in Matteo Berrettini, who is on standby to step into the European line-up if Federer fails to win his fitness race.