Mosimane handed Al Ahly one of their worst defeats at Lucas Moripe Stadium as Themba Zwane, Ricardo Nascimento, Wayne Arendse, Gaston Sirino and Phakamani Mahlambi all got on the scoresheet in a 5-0 victory.
The Brazilians now have one foot in the CAF Champions League semifinals and have made the return leg in Egypt a lot more comfortable.
"If there is anyone of us who could have expected this result I would not be telling the truth," said Mosimane in his post-match interview.
"I didn't expect a result like this. This big team, this is team of the century, this is the biggest team in Africa. But honestly speaking this is football, such things happen in football. As much as the result is huge and a big margin, it is important at this point in time on my side as a coach to have humility and respect for the opponent."
Mosimane was happy that his charges executed their game plan well to come away with a victory against the Egyptian side.
"We played well, we scored the goals, we controlled the game, we played according to the plan," he added.
"I was worried that if I wouldn't have legs to play at three in the afternoon after the big game against Orlando Pirates [on Monday], which was hectic in terms of the demands of the body.
"But at the same time I said it last time that you can't play for Mamelodi Sundowns if you don't look after yourself off the field because the games are heavy and the demands are very big at our club."