Millwall and Leeds United will renew their rivalry on Saturday afternoon and The Lions' boss has labelled the clash a 'great opportunity' to secure the club's first away win of the season.
Millwall took the bragging rights and all three points from the reverse fixture at The Den in September thanks to Aiden O'Brien's late strike.
A near sell-out crowd are expected to descend on Elland Road for the rematch this weekend.
"We have had some really good games against Leeds over the years," Harris told millwallfc.co.uk.
"The atmosphere will be electric. A big crowd, noisy and hostile and those are the conditions that bring out the best in Millwall Football Club.
"We have had a great week's training and we are really confident going into this one.
"Leeds are a really good side and are pushing for a Play-Off place but we have shown earlier this season that we can compete against them. We have to certainly be at our best this weekend because they have some talented players."
Forward Tom Elliott will be available for selection after returning from injury in the U23's goalless draw with Bristol City on Monday, while Shane Ferguson may make his return from a knee injury suffered in December.
"There's a lot to consider and a lot for us to work on but whoever I pick will be ready for the battle," Harris added.
"Shane Ferguson trained this week and Tom Elliott is better. They're both available to come back in which is a big boost for us. A few players have had some knocks and niggles over the past couple of weeks so I will assess how they are recovering.
"But mentally the squad is fantastic, really good. We took a really good point against Preston last week and that shows how far we have come against a top side - a side that has been excellent - but we were also disappointed not to take all three points.
"This weekend is a great opportunity for us. This match is a special one and one we're really looking forward to it."