The Foxes went down to two second-half goals from Brennan Johnson as they lost for a fourth Premier League game in a row following the resumption of the season.
They are just two points above the drop zone in a congested bottom six and Rodgers knows they have a fight on their hands to retain their top-flight status.
Asked whether they were in a relegation battle, the Northern Irishman replied: “Absolutely, let’s not pretend we’re not.
“This is a long season. I have to be honest, if you look at our form and where we are then of course it is a worry.
“But there is still so many games to go and if we can get back the players that gives an extra dimension to our team then we can push on again. But at the moment with what we’ve got is a real challenge.
“It is just the same as what we were earlier in the season. I think before a ball was kicked I told everyone it was going to be a tough season.
“The Premier League is very competitive, you see Southampton the other night beating Manchester City (in the Carabao Cup), it is very competitive.
“But you want to be in it and you have to fight to be in it and that’s what we are going to do.”
In contrast, Forest are beginning to look up after an impressive win that moves them four points clear of trouble.
The result and performance provided a marked contrast from the reverse fixture in October that saw Forest lose 4-0 and boss Steve Cooper claim it was the nadir of his managerial career.
In the days after that result, it was reported that Cooper was going to get sacked, though he actually ended up signing a new contract.
That harrowing loss has turned out to be a catalyst for improvement and was also the source of inspiration for this result.
Cooper said: “I showed a video to the boys before the game of our supporters at 4-0 down at the King Power. I said it’s important that we give a bit back on this particular fixture this week.
“That support meant a lot to me personally, because of the timing of that result and what happened in the week after. Not that I ever think about myself, but for me personally, to give that result back to the fans means a lot to me.
“A lot has happened between then and now, but for it being a local game, and what happened then and today, it is something that gives me a lot of joy.
“We always try and put context around why games can be important. I just thought because of what happened in October and what happened in the week after, it was something we owed back to the supporters.”