Battling to fend off a five-nil Ashes series defeat, England tried bravely to draw a line under the Graeme Swann affair on Wednesday.

Skipper Alastair Cook, celebrating his 29th birthday on Christmas Day with his side under siege from the media and Australia's pace attack, says the Boxing Day Test in Melbourne is the perfect stage for his side to turn things around.

England spinner Swann quit Test cricket on Sunday and threw a hand grenade into the camp the following day as it emerged he had accused some international players of being in danger of disappearing up their own backsides.

The comments were interpreted as an attack on England batsman Kevin Pietersen.

Pietersen said he had been called worse by Aussie crowds in recent weeks, but Swann and Cook both said it was not a case of friendly fire.

"A phone call to Swannie reassured me very quickly that it wasn't at all about any of the England players," Cook said on Wednesday.

"He totally 100 per cent reassures me and the whole England team that it's not about us. So to me, the matter's closed on that."

England trail three-nil in the five-match series, with star pace bowlers Jimmy Anderson and Stuart Broad battling form and a foot injury respectively and wicketkeeper/batsman Matt Prior's place in the team under scrutiny.

Spinner Monty Panesar is expected to return to the side for Swann.

"It's been an interesting week," Cook said.

"Losing the Ashes and with Swannie going as well, it has been a different week.

"When you lose games of cricket, naturally your confidence does slip.

"We're desperate to turn it around and you don't often get the chance to play a Boxing Day Test match at the MCG, which reportedly is going to be pretty much sold out for the first day.

"That's an incredible opportunity we have as players. We know we're up against it in terms of the last three results.

"But you've got to keep believing in yourself."

Cook said he wasn't shocked at Swann's retirement and said the spinner had nothing left to give.

"It's a brave decision. It was quite an emotional chat," Cook said.

Cook said he was encouraged by Broad's bowling in the nets on Tuesday.

"The signs are good," Cook said.