But the gritty centre-back is determined to use a one-off appearance to prove to Posh fans that he is worth a chance at League One level.

Charnock will be recalled to the Posh side tomorrow if former Walsall defender Chris Westwood fails a late fitness test on his sore calf.

He has not started a first-team match since conceding a penalty in the 1-0 defeat at Scunthorpe on August 23. Manager Darren Ferguson blamed Charnock for that loss and immediately placed him on the transfer list to the dismay of the player.

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Match updates: Walsall v Posh.
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Charnock said: "I didn't play well in that game and I made a bad mistake, but it was still very disappointing to be placed on the transfer list.

"I wasn't match fit and I was asked to play in a slightly different position to what I'm used to (right-sided centre-back) so to be told I could leave was very disappointing.

"That was a tough time for me, but since then I've kept my head down, done everything that has been asked of me and I will use tomorrow as a one-off opportunity to put a few things right.

"It looks like I will be playing alongside Charlie Lee and I don't think I've played with him at the back since the pre-season game against Celtic the summer before last.

"But we worked hard together in training yesterday. Walsall have two big, strong forwards, but that will suit me more than playing against nippy strikers and I'm confident we can do well.

"I know I will be left out the following week when Craig Morgan and Gaby Zakuani come back from international duty, but that won't stop me doing my best for the club."

Charnock was a free transfer recruit from Northwich Victoria ln the summer of 2007, but made just 10 starting appearances in last season's League Two promotion-winning campaign.

His progress wasn't helped by a succession of niggly injuries, but he believes he is now the fittest he's been since joining Posh.

Charnock added: "I'm physically fit, but obviously not match fit. I've not had a lot of luck since I came down here and I still have a piece of bone floating around my knee.

"I felt I did well when I played last season, but injuries slowed me down.

"I would have a good run of games in the side and then I would break down again, but I am determined to do myself justice at Walsall.

"It does look like I'm surplus to requirements which is a shame, but I hope to stay in the Football League, ideally with a club back in the North-West."