Al Ahly beat Sundowns 2-0 in the first leg played Cairo last Saturday to put themselves in a strong position to qualify for the Champions League semi-finals.
The Red Devils now need only a draw against the Brazilians, while a 1-0 defeat will also suffice, for them to advance to the next stage of the competition.
However, Mngqithi has since warned his counterpart and former colleague that coming to Lucas Moripe Stadium to sit back could well be their biggest mistake.
"The biggest issue is how they are going to approach the game in Pretoria. They will not last very long if they play with the same intensity that they played with [in Cairo]," said Mngqithi after the game on Saturday.
"I don't think they are very good at defending in and around their box, when they are playing too deep into their half, which is what I think made us have a better second half.
"Because in the second half they did not press us from the top, they retreated and gave us a bit more latitude to get into half spaces and get behind their midfield and also between the lines.
"They are not a good defensive team, they are normally a good offensive team. If they had at come us in Pretoria, I don't see them lasting for 90 minutes."
Kick-off this Saturday is set for 15h00.