Rangers booked their place in the semi-final of the competition when they beat Portuguese outfit Braga 3-2 over a two-legged quarter-final tie.
The Glasgow giants are set to face Leipzig in the semi-final with the confidence of already beating another German side in Dortmund, earlier in the competition and against all odds, under their belt.
However, Miller stressed that Dortmund made the mistake of underestimating Rangers and Giovanni van Bronckhorst’s side outplayed the Bundesliga giants over the two legs of the playoff tie.
He does not expect Leipzig to make the same mistake as they will be fully aware that any team that have made the semi-finals of the Europa League are a good outfit.
The former Rangers star said on Clyde 1’s Superscoreboard: “I think Dortmund underestimated Rangers.
“I think they thought they are a Scottish team, we will go there and we will roll them over, but it never went that way.
“Rangers were the better team over the two legs.
“Leipzig won’t underestimate Rangers.
“You can’t when you get to the last four of any European competition.
“You have to be a good team.”
Rangers will travel to Germany later this month to take on Leipzig in the first leg before hosting them a week later at Ibrox.
