Bayern travel to Spain as strong favourite to progress over the two legs, with Jupp Heynckes' men enjoying a fine campaign.
Domestically, the Germans are running away with the Bundesliga title, while Sevilla are languishing down in sixth in La Liga, 16 points adrift of the Champions League places after a disappointing season so far.
But in Europe they have proven themselves to be a nuisance, having twice drawn with Liverpool in the group stage – including a 3-3 tie in which they battled back from 3-0 down – and eliminated Manchester United in the last round, beating them 2-1 at Old Trafford.
And although they squandered a 2-0 lead in a 2-2 draw with Barca on Saturday, they were the better side for much of the game and were only denied by Lionel Messi's late heroics, with Martinez well aware of the threat they could pose Bayern.
"Maybe people think they're not as good as Barcelona or Real Madrid, but I think they are," Martinez told ESPN.
"If we are not at 100 per cent, they can beat us. It [beating United] is a good example [of what can happen]. I think Sevilla deserved to win both games, in Seville and in Manchester.
"They scored two goals in the most difficult moments of the game [in Manchester]. They acted and played like a big team. That is why they are dangerous. They know how to play important games, they know how to do it."
The atmosphere at the raucous Ramon Sanchez Pizjuan is one element often cited as a strength of Sevilla's and Martinez knows it all too well from his days in LaLiga with Athletic Bilbao.
"They scream very loudly," added Martinez. "When Athletic Bilbao [play there], it's always a good atmosphere.
"It's like a party. I think it will be the same against Bayern because they have to celebrate; they are in the quarter-finals of the Champions League.
"It will be like a party, but they won't give us anything. To beat them we have to fight very hard. Otherwise, we will never win in Sevilla."