Schwarzer was handed a dream finish to the season when injury ruled Chelsea's No 1 goalkeeper Petr Cech out of the club's final push for English Premier League and Champions League honours.

The Socceroos great came on as replacement when Cech badly injured a shoulder early in Chelsea's 0-0 Champions League semi-final first leg stalemate with Atletico Madrid.

At 41, Schwarzer became the oldest player to feature in the knockout stages of the Champions League.

Signed as Cech's back-up on a one-year deal, Schwarzer has barely featured in his first season at Chelsea since moving from Fulham though he did start in Saturday's 2-1 defeat at home to Sunderland.

But he'll now be front and centre in the club's season defining fixtures, the Premier League title-deciding game with leaders Liverpool on Sunday - they trail the Reds by five points - and then the second leg with Atletico on Wednesday at Stamford Bridge.

However, Postecoglou denied temptation to coax Schwarzer out of international retirement announced in November after playing a major role in the Socceroos' World Cup qualification.

With the likes of Club Brugge gloveman Mathew Ryan, fellow young gun Mitch Langerak at Borussia Dortmund and Liverpool reserve keeper Brad Jones in the mix to claim the Socceroos No 1 spot, Postecoglou feels he's well covered.

"Mark made his decision and we've moved on pretty quickly," Postecoglou said.

"We've got a number of outstanding young goalkeepers in our ranks as it is.

"It's great to see Mark getting the chance to play but maybe the fact that he's retired from international duty is why he's still able to do it.

"Being in the national team is a pretty demanding schedule.

"Mark made the wise decision that if he's going to have a year or two more in domestic football he won't have the 24-hour long-haul flights that go with international duty."

While he survived some scares, Schwarzer kept a clean sheet after being called into action against Atletico Madrid, ensuring Chelsea have a home ground edge for the return leg.

"It happened very quickly, but I'm getting used to it," Schwarzer said of his call to action.

"I just tried to do my job but, like all the others, I was up for it."

Chelsea manager Jose Mourinho confirmed Cech's season was over. AAP