MILLWALL will assess defenders Byron Webster and Sid Nelson ahead of Saturday's game with Rochadale.
Saturday's fixture between the two sides will be the first competitive meeting in 50 years and there could be some concern for Harris in the centre of his defence should the pair be unable to play.
Sid Nelson is still recovering from the knock to the ribs he suffered against Crewe, whilst Webster took a blow to the ankle in the final seconds of last weekend's defeat to Southend.
Winger Paris Cowan-Hall is out, however, after he picked up a groin injury in the Elite Development Squad's 4-1 win over Coventry on Monday as his luckless run continues.
Shaun Cummings, who has been out with a hamstring injury has resumed training, but this weekend is a week too early for the defender.
Rochdale boss Keith Hill is keeping team selection discreet as he wasn't forward in offering possible ins-and-outs of his squad ahead of the weekend.
Hill did say, however: "The old Den was intimidating as a player. I played there a couple of times and was a substitute there. You can imagine it; the crowd were on top of it and it was a real task. I don't think anyone wanted to be sub! It was a great place to play though.
"There's no intimidation in these new stadiums; the only intimidation is the opposition as a team really.
"It's a super stadium, but I don't think in these new stadiums that the crowd can generate the type of intimidation that you would get at the old ground."
Sky Bet match odds:
Millwall 6/4 Draw 23/10 Chesterfield 7/4
Probably Milwall team:
4-4-2: Archer; Edwards, Nelson, Beevers, Craig; Onyedinma, Abdou, Williams, Upson; O'Brien, Morison.