Barely a decade on from their famous Premier League title triumph, the Foxes are inside the bottom three of the Championship, one point from safety.
Leicester will also have to overcome a six-point penalty for breaching Profit & Sustainability rules to stay up.
Asked how his old club could've fallen so far, Heskey told Tribalfootball.com: "I'm guessing just mismanagement. Part mismanagement and part ambition.
"The ambition of really pushing into that top four and, and breaking down that elite group. But with that, you have to spend money and I think it was just mismanaged in that sense."
Leicester have sacked manager Marti Cifuentes and hired Gary Rowett as his replacement.
For Heskey, finding someone "who knows the fight" is crucial. Rowett has come in and managed to steady the ship, though is yet to taste victory.
Heskey also said: "It's, it's a really, really tough task, for any manager. I thought they probably need a manager who knows how to set up to just battle.
"At this moment in time, we're in a, we're in a really big battle just to stay in the league now."
Vardy should have stayed
Meanwhile, Heskey believes there will be some regret allowing Jamie Vardy to come off contract last summer. The Foxes legend has since proved himself at Serie A level this term with Cremonese.
Heskey added, "I was one of those ones who was advocating for him to be given an extra year because, look, he was, when he left, he was still our best striker. He still had a lot to give back to the youth players and the players who were there.
"And as you can see now, he still had a lot to give back to the game.
"So I was one of the ones that was advocating for him to stay. But, you know, other things came into play and obviously his age was a major factor within that."
- Emile Heskey was speaking to Tribalfootball on behalf of aGamble