Posh would hate to tackle fellow strugglers Barnsley at London Road (3pm) without the hardest-working and quickest member of their all-star forward line.

But Mackail-Smith is struggling to recover from the hamstring strain that kept him out of the Carling Cup defeat at Blackburn on Tuesday.

He will have a fitness test ahead of the Barnsley match, but he's prepared to play through the pain barrier if he gets the nod from the club's medical staff.

Central defender Gaby Zakuani will definitely return to the side tomorrow, but Charlie Lee has been ruled out after suffering ankle ligament damage at Ewood Park.

Lee will be out for a fortnight which could open the door for new signing Ryan Bennett to make his competitive debut at right-back ahead of out-of-form club captain Russell Martin.

Mackail-Smith: "I desperately want to play tomorrow because it is such a vital game and I feel we are on the verge of an excellent run of results so I want to be involved in that.

"I turned my ankle in training on the Thursday before the Scunthorpe match so I wasn't fully fit for that game and then I tweaked a hamstring during the game so I've had to have loads of treatment this week.

"We'll leave it as late as possible before making a decision on whether I play or not and if I don't make it I'm sure we have adequate back-up to get the result we need."

Live match coverage: Posh v Barnsley.

Posh manager Darren Ferguson confirmed a fitness test for Mackail-Smith will be held tomorrow afternoon. If the results are negative, Shaun Batt could start the game up front alongside Aaron Mclean.

On-loan goalkeeper Ben Amos from Manchester United will start tomorrow after completing his one-month loan move to London Road yesterday. He will deputise for suspended number one Joe Lewis with James McKeown on the subtsitutes' bench.

Ferguson said: "Craig is a bit of a doubt, but he's such a key player I will leave it as late as possible with him. We are hoping he will join in training today, but we will be careful with him to give him the best chance of playing.

"Charlie is struggling though. That was a bad tackle the other night, but I have options at right-back with Russell Martin, Chris Whelpdale and Ryan Bennett. Ryan played well, albeit at centre-half, for the reserves on Wednesday.

"Ben will definitely play in goal. It's not the right time for James McKeown yet."

A win for Posh tomorrow would take them above Barnsley on goal difference ahead of a difficult programme of Championship fixtures in November when Newcastle (away), Sheffield United (away) and Middlesbrough (home) provide the opposition.

Barnsley are giving late fitness tests to former Liverpool winger Adam Hamill and Icelandic midfielder Emil Halfredsson.

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