Nkosinathi Sibisi scored the only goal of the game at the Old Peter Mokaba Stadium with 67 minutes on the clock.
The result left Pirates 12 points behind league leaders Mamelodi Sundowns but with three games in hand.
While Riveiro was happy with the win, he bemoaned the state of the playing surface at the venue that hindered both teams' play.
Speaking after the game, Riveiro told SuperSport: "I think it's always an ugly when you play at the Old Peter Mokaba, there's only way, the state of the field is terrible, slow, bumpy, not a football ground, so you have to find a way to not concede and be patient and wait for opportunities.
"We had a lot of quality and opportunities this time came in a set-peice, massive three points, so happy to collect three points because not everyone can do it, against a very disciplined team that today was running an extra mile, happy with three points."
Riveiro added that he doesn't expect the news of his departure at the end of the season to have an impact on his team.
Pirates are in contention for the Premiership, as well as the Nedbank Cup and CAF Champions League.
The Bucs boss added: "They want to win, they have been showing they want to win since day one this season, nobody can say the opposite, they wanted to win the game, we spoke at half-time, we felt it was coming, we had to be patient, we had to continue and in one of those chances, one set-piece or special situation we need to capitalise and we defended well.
"We're playing every game at the limit, three more points, now we have to go to the Champions League, then another final in the Nedbank, like I said before the game, it's the consequence after being competitive since day one.
“These players, this group, this coaching staff, they are doing wonders this season, let's continue until the end.”