CHESTERFIELD have made a solid start in Sky Bet League One after their play-off semi-final defeat to Preston last season.
They sit ninth in the table, but Millwall could pull level with Dean Saunders' side should they win their first game at The Den this season.
Like the Lions, Chesterfield have also played Barnsley and Shrewsbury this season. They, too, won 2-1 at Greenhous Meadow but beat Barnsley 3-1 at home.
And like Millwall they were indebted to their goalkeeper in the 0-0 stalemate at home to Rochdale last weekend. Tommy Lee produced a number of important saves to earn his side a draw and Saunders reckons he is worth 15-17 points to the Spireites.
Saunders believes Harris could have done with a good start to buy some time to perfect his approach, but knows what to expect from a side managed by Millwall's record goal-scorer.
"What he needed really was three wins and that would have given him six weeks (breathing space) to get them all organised," Saunders said. "He'll feel under a bit of pressure now to get the team like he wants it but it takes time.
"Sometimes it can take two or three years."
"He worked his socks off (as a player) and he'll have his team doing that, so that's what we can expect and that's the bare minimum from us. There's no reason why any team should out-work us.
"We're fit, as fit as any team in the league. The lads can match anyone work-wise and then hopefully the skill will shine through.
Harris, meanwhile, is unlikely to recall Joe Martin despite the full-back returning to training this week as he is short of match practice, while Carlos Edwards won't be included until next week after he rejoined the Lions on Monday.
Shane Ferguson is also out with a hamstring injury, but Sid Nelson should be okay after he picked up a dead leg at Glanford Park.
If he recovers then Harris is likely to stick with the same back four that kept a clean sheet last week.
Jordan Archer will continue in goal and Nelson was glad that the former Tottenham keeper was the last line of defence against the Iron.
"Jordan played really, really well at Scunthorpe but Fordey's been helping him a lot," Nelson said. "You can see in training how good Jordan is."
Harris told the club's official website he is pleased with the progress of teenagers Nelson, Ben Thompson and Fred Onyedinma and welcomed the longer preparation time he had with his squad before Saturday's showdown.
"The young lads have done extremely well," he said. "We all want to see a young and vibrant side with a good mix of senior players also, so it's getting that blend right.
"It's been nice to have a free week to work on a few things to get the boys into some sort of routine and rhythm.
"We're refreshed and ready to go."
Sky Bet match odds:
Millwall 6/4 Draw 23/10 Chesterfield 9/5
Probably Milwall team:
4-3-3: Archer; Cummings, Nelson, Beevers, Craig; Abdou, Williams, Thompson; Onyedinma, Gregory, Morison.