Martina Navratilova expects Rafael Nadal and Novak Djokovic to be the dominant forces in men's tennis in the coming years, insisting it is "difficult to see" Roger Federer reclaiming the number one spot.
Federer has established himself as one of the game's all-time greats, winning 16 grand slam singles titles - a record for a male player - and at one point holding the top ranking for 237 weeks in succession.
But he has fallen to number three after his defeat in the BNP Paribas Open semi-final against Djokovic, who went on to beat Nadal in the final of the Indian Wells event.
"He lost in the semi and Djokovic beat Nadal in the final, so Djokovic is certainly playing great tennis," said Navratilova at the launch of the Liverpool International Tennis tournament, which takes place from June 16-19 and is in its 10th year.
"Roger is on the other side of the float, I don't think he'll ever play as well as he did three or four years ago - that's not to say he can't still win a slam, but it's difficult to see him climbing back to number one.
"Nadal is dominating and Djokovic's confidence is off the chart. Roger has lost three matches (this season) to Djokovic and lost to him at US Open last year as well, it will get under his skin ."
Navratilova also had words of warning for British number one Andy Murray, claiming a change in mentality is needed if he is to fulfil his potential and win a grand slam tournament.
The British number one has reached three grand slam finals - the Australian Open both this year and last, and the 2008 US Open - but has failed to even win a set across the three matches.
Navratilova said: "I would have though he would have won a slam by now, though he still has plenty of time on his side.
"He's still in his prime but with every year it gets more difficult, the expectations and the pressure get higher.
"He's got the talent but he's got to get tougher on himself mentally - he's too quick to pass the blame, looking at his box and yelling at them as if it's somehow their fault he missed that forehand.
"Also, he doesn't give his opponent enough credit. He gets mad when he gets aced - that's a good serve, too good. He needs to change his attitude, to give his opponent more credit which takes the pressure off him."