The Phobians have suffered their worst start to the Ghana Premier League season since 2013, picking only nine points in their opening seven games. They were handed a 2-1 defeat by city rivals Tema Youth on Wednesday.
Kotoko, on the other hand, are without a defeat this season, and tied on same points with leaders Aduana Stars but Opeele insists form doesn't count in the Super Clash.
''Hearts of Oak will definitely defeat my former club Asante Kotoko in Accra on Sunday because current form of both clubs are not a factor to consider in such games," Opeele said Asempa FM.
"Kotoko will definitely lose that game because Hearts have some fine players and character and everything points to their direction this time around. It will surprise many people that I am making this pronouncement because of my affiliation with Kotoko in the past but that is my expectations from the game.
"I trust the players of Hearts to thwart the efforts of Kotoko and shock majority of Ghanaians on Sunday," he added.
Hearts are winless in their last three meetings with Kotoko at home, scoring only one goal in the process.