Brad Gilbert says recent criticism of Andy Roddick is unfair.
Roddick suffered a surprise fourth round defeat at the Australian Open
The American has not won a Grand Slam title since the 2003 US Open and recently went out of the Australian Open in the last 16.
But Roddick's former coach Gilbert told BBC Sport: "More than anything, his situation is about how much better Federer has been since 2003.
"He's like the Tiger Woods of tennis. Without Federer, Andy would be winning a whole lot more tournaments."
Federer has ended Roddick's Wimbledon hopes for three years in a row, including the last two finals.
"Let's remember, Andy is still number three in the world," said Gilbert.
"The two in front, Roger Federer and Rafael Nadal, are outstanding players, and Andy is only 23, a year younger than Federer, so let's give him time."
However, the American's recent Grand Slam form has led some to question his surprise decision to end an 18-month association with Gilbert at the end of 2004.
Roddick suffered a shock first-round defeat to Gilles Muller in the first round of September's US Open and went out in the fourth round of the Australian Open to Marcos Baghdatis.