Masandawana are hosting Usuthu coming from a humbling 4-2 friendly loss to the Glamour Boys last weekend.
The value of the Shell Helix Ultra Cup is debatable, but Karuru does not believe it did not affect the Sundown players, who were still playing for pride.
"They are hosting us as wounded lions because they lost 4-2 against Kaizer Chiefs, even though coach Pitso Mosimane fielded players that are not playing every week," Karuru warned.
"It was a good chance for them to show what they can give. Now we don't know which team they will field because we don't know which players impressed them.
"Against us they wouldn't want to lose, because they already lost a cup, because the fact is a cup is a cup, whether it's a friendly match or not. Teams like Sundowns want to win cups. I'm sure they are gunning for this one, it's going to be a tough game and we are prepared for it."
Meanwhile, Usuthu coach Jozef Vukusic believes his side needs to be on top of their game to unsettle Pitso Mosimane's team.
"If you want to beat Mamelodi Sundowns you need to play on your limit and potential, but a draw would be enough and then go to penalties. So it's a cup game and someone must lose. We will try our best in that game.
The Serbian coach also played down their defeat to Amakhosi last weekend.
"In this game they will come with a different ambition to do well from that last performance. You know teams like Sundowns want to win every single game in the league and cup. They have a big squad, they can use many players, they are used to playing many games."