Usuthu won the reverse fixture in October with a come-from-behind 2-1 win courtesy of goals from Nomvethe and Khenyeza at Loftus Versfeld.
"They are very important to us," Mnguni says of the experience forwards, who have both scored over 100 PSL goals.
"They know how to read a game. In the last game we played against Sundowns Nomvethe told us he was going to score because they were taking us for granted. He came as a sub and scored a goal, him and Mabhuti. So they have more influence to win games."
The Newcastle-born Mnguni says the team are preparing as per normal for the contest at King Zwelithini Stadium.
"The feeling is okay as usual, we just need to be more prepared. It's a big team that has support everywhere. Ja, we know their style of play and everyone in the team has that mentality of beating them. So I think that's a good team spirit. Everything is okay as we are all happy."
Usuthu are currently 10th on the Absa Premiership table with 27 points from 22 matches and fighting for an MTN8 ticket, while Sundowns will look to stretch their four-point advantage at the summit.
"Yes, for sure they are [in need of points], as we are in need of points also. We expect that they will come at us from the first second of the game. So as AmaZulu we are playing at home, it won't be easy for them to go with three points. We need to put in 150 percent because we can plan but without more effort it won't be easy to beat them."