Javi Martinez is wary of Bayern Munich's Champions League opponents Atletico Madrid, saying they are "the toughest potential semifinal opponents."
Martinez, 27, joined Bayern from Athletic Bilbao in 2012, and during his six years in the Spanish top flight he played in 13 matches against Atletico, with the side's current boss, Diego Simeone, in charge during the defender's last La Liga season.
The Spain international, who scored three of his 22 La Liga goals in matches against Atletico and recorded five wins and eight defeats, warned that the passage to the Champions League final in Milan will not be easy.
"They're one of the best European teams in defence. All 11 men on the pitch play their part in it, from the strikers to [Jan] Oblak between the posts," he said on the club's official website.
"They're dangerous on the break with quick players like [Fernando] Torres, [Antoine] Griezmann or [Yannick] Carrasco. They have players with good passing qualities like Gabi, Koke and Saul [Niguez]. Atletico play very aggressively."
Bayern and Atletico boast the two best defensive records in the European top flights.
However, whereas the Germans look to control possession, the Spaniards, particularly in the big games, wait for the counter, and hand the ball to their opponents like in the Champions League quarterfinal against Barcelona, where they only had 28 percent of the ball.
Martinez said: "It's a mixture of aggression, focus, good play and mental strength which makes them so strong. They're a coherent team. We have to give 100 percent, full throttle!"
Real Madrid and Manchester City contest the other Champions League semifinal, and Martinez would have preferred to play against either side.
He said: "Atletico are the team against which I least wanted to play. They're hard to beat, for me personally they're the toughest potential semifinal opponents."
This sentiment was echoed by his teammate Thiago Alcantara, who said: "Two teams on a par face off. We're in for a tough match in which we'll have to go to our limits."
Veteran midfielder Xabi Alonso added: "We have to be clever. We know that we'll play at least 180 minutes, but we won't play for a draw in Madrid. It's our mentality to go for a win."