Savour Rafa & Roger - Roddick

Tennis fans should savour every moment of Roger Federer and Rafael Nadal's domination of the sport because such champions do not come around very often, world number eight Andy Roddick has said.

The American is preparing for the ATP World Tour Finals where he will face world number one Nadal on Monday in his debut at London's O2 Arena having had to sit out last year's showpiece tournament at the spectacular indoor venue because of injury.

"Rafa has had an unbelievable year," Roddick said of the 24-year-old Spaniard who has won three of the year's four grand slams and could hold all the majors if he wins the Australian Open at the start of next year.

"What he has done is unreal. To put it into context what Roger and Rafa have achieved for the past five years I would hope that people appreciate it because I guarantee people will be writing in 15 years time that these were the good old days."

Looking ahead to his opening round robin clash with nine-times grand slam champion Nadal, Roddick said he was just glad to be involved in the season finale after the second half of his season was dogged by illness and injury.

He is also looking forward to a warm welcome from the British fans who have taken the Texas-based former world No.1 to their hearts after his three Wimbledon final defeats at the hands of Federer -- most notably 2009 when he lost an epic encounter 16-14 in the deciding set.

Roddick watched from the stands last year at the O2 and still remembers with pride the ovation he received when he was captured on the video screen inside the arena -- a moment he described as one of his most memorable.

"It's strange because it's a polarising event for the crowd here, I normally get a really good reception but then a tournament like this comes along and I've got Rafa in the first round so I can't take that for granted" Roddick, who beat Nadal in Miami this year, told reporters.

Roddick injured an adductor muscle in Shanghai in October and admits that he feared his hopes of qualifying for the year-end tournament for an eight time had gone.

"I felt pretty clean and played well at the beginning of the year but then I got sick and tried to play through it more than I should, then I got injured. So to be here at the end is a little bit surprising.

"I feel fine now though. I didn't know what I was going to bring to the table in Basle and Paris but I managed to sneak out some results and only lost to the guys that won the titles."