Mark Schwarzer knows the day will come when his body screams enough is enough. His limbs will protest as he edges out of bed in the morning, the very thought of venturing into the chill of a winter drizzle to roll around in a muddy goalmouth enough to bring on all the aches and pains associated with the onset of middle age. It is just that, even with wisps of smoke still drifting from the candles on his 40th birthday cake, the Australian remains convinced that moment remains some way off. He still has too much to achieve.

If Saturday was about celebrating becoming a quadragenarian then, at St Mary's this afternoon, Fulham's veteran will fling himself into a Premier League contest with the same vigour that marked his top-flight bow, for Middlesbrough at Sheffield Wednesday back in 1997. This will be his 475th game among England's elite, yet he is still hoping to add significantly to that tally and, in turn, his hundred-plus caps for Australia, having targeted a swansong at the 2014 World Cup in Brazil. He is a stalwart of two clubs with whom he has graced Europa League finals but a goalkeeper still chasing the dream of the Champions League. "They say you know when it's time to step aside," he says. "Maybe I will but I've got goals ahead of me. It's all part of the grand plan."

That strategy formulated early. It started back in Richmond, New South Wales, when he turned out for Colo Cougars' under-sevens and the local butcher reminded Schwarzer's mother, Doris, that "soccer is for softies"; or as a 10-year-old when he took up goalkeeping; or at 19 when he first donned the shin pads he has worn for games ever since. But, over a 22-year professional career that has taken him from Marconi Stallions to Teesside, via spells with Dynamo Dresden, Kaiserslautern and Bradford, and into a fifth season at Fulham, Schwarzer remains thirsty for more. Paulo Gazzaniga, who will shake his hand at Southampton today, is half his age but would do well to learn from the softie turned sporting icon in direct opposition.

Longevity has offered Schwarzer a sense of perspective. Nothing seems to faze him, eager as he is to dissect everything from Australia's sporting crisis to gamesmanship or Fulham's summer of upheaval. The London club were in the bottom division when Schwarzer arrived at Valley Parade yet, like the goalkeeper, they are now established in the elite. Even so, there had been flutters of concern when Mousa Dembélé and Clint Dempsey departed for Tottenham Hotspur before the transfer deadline. "The situation was very disruptive," he says. "We played West Ham the day after the window closed and were very poor. The whole thing had unsettled us. But the guys who have come in have helped pick us up. They've all added quality and Dimitar Berbatov has given us something extra. Something we didn't have before.

"Whenever any player comes to the club you wonder if he'll fit in and flourish and if he'll reproduce the form he'd shown previously. But you could see straight away in training that the guy has amazing talent. It was just a matter of how long it would take him to gel with the team and Dimitar's settled in almost instantly and been outstanding: his commitment, his skill and vision on the ball, and the demands he makes of others. The younger players in particular, he's hard with them but also quick to praise them if they do something well. That's something we'd lost.

"We've lacked a bit of that, demanding players to produce at a high level. Berba's developed that attitude at Tottenham and Manchester United, expecting the best from everyone, and he's brought it here. As experienced players, we set the standard. Some would say the young guys get in too easily these days and then get carried away with themselves. It's our job to knock them down a couple of notches sometimes, give them a reality check, to get the best out of them. The whole club has to maintain momentum and evolve the style of football the manager wants. We've been too one-dimensional at times. The manager is changing that."

Others have found that process unacceptable. Bobby Zamora endured a fractious relationship with Martin Jol last season and was one of six high-profile departures from Craven Cottage this calendar year. Last week, while Queens Park Rangers loiter at the foot, the former England striker suggested "the vast majority of players there now" are unhappy with Jol. "Bobby had his issues with the manager and that's why he moved on," says Schwarzer. "If people had a problem with the manager, you wouldn't have seen the successes or the performances we've shown so far this season. It would be impossible to do that. The players are all 100% behind the manager and, as far as I'm concerned, there's no validity to [Zamora's] statement at all."

No other foreign import has played as many Premier League games as Schwarzer. So what had he made of Sergio Agüero's comments after Manchester City's victory at Fulham last Saturday, the Argentinian suggesting domestic referees are more sympathetic to local talent when it comes to players tumbling in the penalty box? "I dive all the time and get nothing for it, so I fully understand what he's on about," says the goalkeeper with a grin. "Seriously, he spoke about the penalty that was given to us [being soft], and that was won by John Arne Riise, so maybe he's got his nationalities a bit mixed up.

"Certain players tend to dive each week more than others and, all of a sudden, that reputation sticks. A lot of the time these guys have got only themselves to blame for having the odd call go against them because they're known for theatrics. I've played against 'foreign' players – I'm not naming names – who call for everything and anything that comes in the box."

Has he not encountered English players going to ground too easily? "To a lesser extent because I don't think it's in their nature. The English mind-set – the Australian's mind-set is very similar – is be hard but be fair. Players from different regions of the world view the game in different ways. Some see it as life and death and will do anything to win. I've played against teams from South America and Asia and some players will do whatever they possibly can to get a result or a decision. If that means cheating, they will. I've seen them. There are different codes of ethics all over the world. We talk about 'fair play' but one could argue some players are countering that by not playing in the spirit of the game."

The goalkeeper experienced gamesmanship first-hand in the second leg of the World Cup play-off in Montevideo in 2001, when Australia were spat at, punched and robbed on arrival. On the evening of the game the rendition of their national anthem began mid-chorus, stopped, restarted and then fizzled out prematurely. The visitors were intimidated and duly overwhelmed. Four years later, again in a play-off, Guus Hiddink's team welcomed Uruguay to Sydney and three opposing players set upon the Socceroos' centre-half, Tony Popovic, in the tunnel. "They knew he was hot-headed and might react. But to see them going for him … I can't fathom that. I don't know how I'd react if my manager told me: 'Go up to the other goalkeeper, pin him up against a wall and say something about his mother.' I couldn't do it."

Australia prevailed that day, Schwarzer saving penalties from Dario Rodríguez and Marcelo Zalayeta in a shoot-out to propel his country to a first World Cup finals in 32 years. It remains his finest hour, an image of his decisive save engraved in the cut-glass trophy presented to him when he became the first Australian to accrue 100 caps last month. That occasion was in the unlikely setting of Beirut's Saida Municipal stadium in front of a crowd of 9,000, his team-mates wearing training gear with "Schwarzer 100" emblazoned in fluorescent yellow in the warm-up and Lucas Neill tossing him the captain's armband just before kick-off. "To be the first to reach that landmark makes it all the more special," says the veteran, even if that friendly victory was unrepresentative of recent form, with the Socceroos having endured a stumbling start to their World Cup qualifying campaign. "This is a transitional period. The reality is our success hangs on the quality of the players coming through and we need them to step up."

The same could be said for Australian sport in general. Schwarzer enjoyed the Olympic Games this summer as a spectator, spending time at the beach volleyball and in the aquatics centre. His compatriots were expected to claim gold in the men's 4x100m freestyle relay on the night he went, only to finish fourth. To end 10th in the medal table, with only seven golds, felt inadequate. "By our high standards it's a crisis. There's been a really rough patch over the course of the last few years. It's starting to boil a bit. There are a lot of questions to be answered, especially after the Olympics. But when you consider the reality, it shouldn't come as a surprise.

"Look at the implications of funding having been cut back, as it has since Sydney in 2000. At one point during the Olympics, out of all the gold medals that had been won up to then, 18 had been by athletes coached by Australians. So we've exported our best coaches. We've got only ourselves to blame. It's very difficult to demand that success if you're not putting everything in to achieve it. Great Britain, like most host nations, threw a lot of money at it. Results speak for themselves. But it'll be what happens next that is interesting."

The same applies to Schwarzer. The goalkeeper is out of contract next summer, with David Stockdale kicking his heels waiting for a chance to impress, but hopeful he can remain in England. He has his own ambitions: hoisting Fulham firmly into European contention; maybe even gracing the Champions League. That chance looked to have gone when he turned down Bayern Munich and Juventus to move to Craven Cottage in 2008 and again when the club rebuffed Arsenal's inquiries two years ago.

"It's still a dream," he adds. "When I first moved to Fulham I thought it couldn't get any better than this and then you're linked to a club like Arsenal which was very flattering. The club were adamant I wasn't going anywhere and it's nice to be in that situation too. You can never say 'never'. It keeps you on your toes, having that desire in the back of your head. Whatever happens next summer, I'd love to stay in England. All I'm focusing on is playing well for Fulham, winning games, having a good season and qualifying for the World Cup with Australia."

Those are immediate objectives. The aches and pains can wait.