The Portuguese were leading 2-1 in Lisbon last September with just four minutes to go, but goals from Christian Poulsen and Daniel Jensen completed a remarkable turnaround for the Scandinavians.
Since that match, Morten Olsen's men have gone from strength to strength and sit at the top of Group 1, seven points clear of Portugal. But Tiago has warned Denmark can expect to face a much different opponent in Copenhagen tomorrow night.
"That match (against Denmark) was all too easy for us, for 80 minutes anyway," said the Juventus midfielder. "We were playing good football and I don't think it had entered our heads we could lose that match.
"But we have a new coach (Carlos Queiroz) and new players in the squad, and we're far more of a team now than we were. We're definitely stronger than a year ago."
Denmark winger Jesper Gronkjaer believes a draw would be good enough for his side to end Portugal's challenge in their pool. "I believe and hope for a good result, because we're in a good position and because we don't want to have to go chasing a result," he said. "With a point, we can more or less knock Portugal out of the way so the optimism is high."
Erwin Koeman's side face Sweden in Budapest tomorrow, and Balazs Dzsudzsak is hopeful they can record their fifth successive win in qualifying - if they can contain the threat of Kim Kallstrom.
"We've watched him on DVD, he's a dangerous player and bosses their midfield," said the PSV Eindhoven winger. "We've looked at Sweden's strengths and weaknesses, and Kallstrom is one of their strengths. At this moment in time I don't exactly know how we're going to stop him, but we'll be given instructions about it before the match."
To add to their troubles, coach Lars Lagerback has doubts over the fitness of star striker Zlatan Ibrahimovic, with the Barcelona man struggling with a knee injury.