The Dons secured a famous 3-0 win in Croatia last week against a side which had not lost in 12 home legs in Europe, but the visiting players were given ample warning of Rijeka's threat during a difficult opening half hour.
Rijeka drew 3-3 in the league on Sunday and their list of conquests in Europe in recent years, which includes Stuttgart and Feyenoord, means there will be no complacency at Pittodrie.
"They are more than capable of scoring three goals," said McInnes, whose side face a likely trip to Kazakhstan to face Kairat Almaty if they progress.
"They have shown that over the last few years in Europe. They have dealt with a lot of good sides.
"They were huge favourites in the home tie and they were huge favourites to go through into the next round, and they are more than capable of scoring three goals.
"They scored three goals in the league on Sunday and they could have had a few goals before we scored over there.
"They have enough attacking threat and a style of play that will always allow them to get chances. But we have to limit that and make sure we make the most of our own opportunities.
"We're going to have 17,000 fans behind us and hopefully we hear them and they help us get the job done because it's important we start the game properly and take the confidence from last week into this game."
Aberdeen refused to sit in after Andrew Considine headed them in front from a corner last week and McInnes will not allow his players to drop off at home.
"We don't want to defend, defend, defend and just try to get through the 90 minutes," he said.
"There has to be an onus on us to be rigid but also still show that we are an attacking threat.
"We did that well enough in the away tie but it's only half-time, and 3-0 leads can quickly go after half-time in a tie when there's 45 minutes to go, never mind 90 minutes."
Source: PA Sport