PETERBOROUGH director of football Barry Fry says he is delighted to see Shaun Batt fit and playing again ahead of the striker's return to London Road.
Batt was sidelined for over 18 months by a nasty knee injury sustained just weeks after joining the Lions from Posh in June 2010 and has yet to face his former club, for whom he made 60 appearances.
But the 25-year-old is expected be in Kenny Jackett's squad for Tuesday's Championship clash between the two sides and Fry is wary of the frontman's ability to be a match-winner.
He told NewsAtDen: "Shaun was a fantastic impact player for us. His pace always created problems for the opposition.
"He was unlucky not to start more games than he did. The problem with being a utility player is that sometimes a manager uses you from the bench to change games.
"He wanted to move back to London and was absolutely delighted to sign permanently for Millwall. He was really looking forward to it and then he had that horrendous injury.
"Everybody at Peterborough, the management team, the players and the fans wish him well. It could come back to haunt us a bit because we know he could be the difference between winning and losing tonight.
"We're delighted he's back playing again. Millwall fans haven't seen the best of him yet but when they do, they'll love him; he gives 150 per cent and will run through brick walls for you.
"He's a great lad and he's really looking forward to repaying Millwall because he tells me they've looked after him very well."
Millwall, who have not lost their first two matches of a league season for 30 years, travel to Peterborough on the back of an opening-day defeat to Blackpool.
But Fry knows that the Lions will provide a stern test for Darren Ferguson's men, who have spent close to £1.8million on new players this summer.
"We've got the smallest budget in the Championship by a million miles but I'm sure Millwall aren't far above us," Fry added.
"Jackett over-achieves every year and what he has done there has been quite outstanding. It's incredible really. We know with him in charge it will be a very difficult game."