“We earned it,” said Mosimane.
“I said this during the week, that it would be a tough, tactical match and that’ s how it happened.
“We had to fight, and we worked hard for it but we earned it.”
Downs dismissed their neighbours from the Telkom Knockout after goals from Themba Zwane and Elias Pelembe, while Tuks’ solitary strike came from Geofrey Massa.
The match could not be decided in regular time and Pelembe took advantage of extra-time to net the winner for Sundowns.
It was Downs’ fourth consecutive victory in all competitions and Mosimane said it will be important to build on their newly found form.
“Last season I think we managed to go 10 games unbeaten,” said Mosimane, “so we know how it feels. We must continue working hard and I think I have played the same team for the last four matches and it has been producing results.”
Tuks coach Steve Barker said the loss will inspire them to pull their weight against cross-town rivals SuperSport United in a league match on September 18, after the international break.
“For clubs like ourselves the league is the most important part,” said Barker.
“Any good cup form or cup run is an added value. We wanted to do well in this cup.
“But am pretty sure if we double our efforts we will do well against SuperSport.”
The last-eight draw of the Telkom Knockout will be held at the PSL offices on Monday.