Pirates lost 4-1 to Downs in a league match last weekend at Loftus Versfeld Stadium, failing to close the gap between them and the Brazilians.
The loss now sees the Bucs trailing Downs by nine points, with the Brazilians having collected 42 points in 15 games, while Pirates have managed to secure only 33 points.
Despite the defeat, Riveiro believes his squad is still strong and that they could have easily won the match had they taken their goal-scoring chances. However, he acknowledges that Sundowns were the better side on the day.
"The difference between the two teams will show at the end of the season, after 30 games," said Riveiro.
"Then we will see if we are on the same level, or if the difference is big, or if it's not. But today [Saturday] is just one game.
"The game can go in different directions. If we had scored in the first half, although in my opinion, Sundowns were better than us."
Orlando Pirates clinched the Carling Knockout Cup in dramatic fashion at the New Peter Mokaba Stadium, edging Marumo Gallants 1-0 after extra time to secure their second trophy of the season.
Marumo Gallants' goalkeeper Washington Arubi says his side is comfortable being labelled the underdogs ahead of Saturday's Carling Knockout final against Orlando Pirates.
Orlando Pirates face Marumo Gallants in the Carling Knockout Cup final at Peter Mokaba Stadium on Saturday as they attempt to win their second trophy this season.
Orlando Pirates captain Nkosinathi Sibisi is keeping his focus sharply on the Carling Knockout Cup title as his team tops the Betway Premiership table with 28 points after 12 games.
