Riza said if it were not for the fans, part of him would have preferred to have been knocked out in an earlier round.
“It’s great for the fans, a good moment for them,” said Riza.
“They’re really happy about the fact we’re in the fifth round and going to Villa. There’s 6,000 fans going which we’re really happy with.
“I want to win and get to the final, but are we really going to do that?
“Sometimes I think it would have been best if we went out in the third round, but then you look at it and say, ‘Look what we’ve given the fans’.
“I speak to lots of them and they are so excited about this game, and that’s why I’m disappointed we can’t be at full strength and have a real go at it.”
Despite Riza’s frustrations, spirits will be high in the Cardiff camp after a crucial midweek win over Hull City, which lifted them above the Tigers in the league.
Aston Villa meanwhile suffered a 4-1 loss at Crystal Palace on Tuesday, and are likely to rest some players before their Champions League last 16 match with Club Brugge.
And while naming a full-strength team may not be possible, Riza said “nothing was impossible” when it comes to the result.
“It’s going to be a very tough game, but nothing is impossible in football,” said Riza.
“They will still have a full team of internationals on the pitch, that’s the depth they’ve got.
“We have to manage the game accordingly and correctly. We have to approach it in a way where we’re not easy to break down and use the ball diligently.”
