By Steve Keating

MONTREAL (Reuters) - Roger Federer celebrated his 30th birthday in typical low-key fashion on Monday but the Swiss tennis great has no intention of fading quietly away from the game.

Federer will begin to answer that question this week at the Rogers Cup. Still number three in the world rankings and an opponent others still want to avoid, Federer's 30th hardly had the air of a retirement party.

Certainly, no one views this season as the end of the line for the "Federer Express" but he is steaming into treacherous territory.

Andre Agassi, Pete Sampras, Jimmy Connors and Federer's childhood hero Rod Laver all added to their Grand Slam totals in their 30s but more tennis careers have sputtered to inglorious ends than soared to new heights.

Federer spent 285 weeks at the top of the world rankings and Connors, for one, does not see any reason why the Swiss maestro could not be number one again -- if he is willing to pay the price.

"I think Federer, at 30-years-old, still is young," Connors told reporters. "Certainly if he's willing to put in the time and do what it takes, I don't see why not (be number one again).

"But now it's not just one guy he has to beat. He has (Novak) Djokovic, (Rafa) Nadal, (Andy) Murray, a host of guys that are coming up and are looking for his scalp.

"You have to look within yourself: 'I was number one, I'm tired of being number two or number three. It's time for me to get back to where I belong'.

"Then you sit down and you figure that out. Are you willing to do that?

"If you're willing to do that, then the work and everything that he puts in certainly will pay off."

But with 16 Grand Slam wins, an Olympic gold medal, a bulging trophy case and bank account, motivation will be the key to Federer adding to his legacy.

"When you get older, that means you just have to work harder, put in the time," said Connors. "Your life changes along the way.

"He has to remember the one thing that has gotten him to this point is his tennis."

(Editing by Peter Rutherford)