Former world's no.1 and tennis great Pete Sampras believed Roger Federer can give up to four more years of competitive tennis, and could perhaps add another Grand Slam to his already impressive trophy haul.

In an interview with the Guardian, Sampras pointed out that Federer can still compete with the best in the sport because he still shows the same fire of competitiveness and love for the game despite his advanced age of 33.

"He's got a true love of the sport, doesn't mind the travel, doesn't mind the lifestyle. He seems to enjoy it. I'm amazed he finds the motivation to play the outside events, although obviously the majors are his main motivation. I found myself getting tired when I hit about 30, 31 - he's still enjoying it.He could play another three or four years," Sampras said in an interview with the Guardian.

Although Federer may no longer have a shot at cracking the top of the world's tennis rankings, Sampras believed the Swiss tennis star will remain a force to be reckoned with in every Grand Slam championship, especially the Wimbledon Open, where he believes Federer has a chance at winning his eight title at All England Tennis Club this year.

"If Roger feels that he can't compete at the highest level, I don't see him playing just to play. He'll play for the majors and maybe to be No. 1," Sampras said.

Before he closed the interview, Sampras said that he believed Federer will continue to play strong for the remainder of the season, despite bowing out to Nadal in straight sets in the semifinals of the Australian Open championship in January.

"He struggled a little bit at times, although Rafa's just a rock. But I do see Roger building from that. I think he's going to have a good year. Obviously the French and Wimbledon are his next main goals, and I do think he can win another major," added Sampras, who has 14 Grand Slams around his belt.