Guardiola takes over as City boss next season after three years at Bayern in which he has steered the Bavarian giants to the last four in Europe on each of his three years in charge.
“Spanish teams are always strong in the Champions League and I have seen in the last few years how strong Atletico are in the Spanish league,” Guardiola said.
“They have a good mentality under their coach (Diego) Simeone and have good players going forward in (Fernando) Torres and (Antoine) Griezmann. Simeone is one of the best coaches in the world and his team is one of the best in Europe.”
Atletico, winners over defending champions Barcelona in the quarter-finals, and Bayern have met once before in European action, in the 1974 final. The Bundesliga side ran out 4-0 winners in the replay following an initial 1-1 draw.
Bayern striker Robert Lewandowski said the Bundesliga team would be wary of Atletico.
“@Atleti did show the strength in the match with Barcelona. We must maintain maximum concentration,” the Polish international tweeted.
Bayern’s Spain international Javi Martinez added: “That will be a difficult game against a strong opponent.”
Clemente Villaverde, Atletico’s director of football, called on his team to “maintain that reliability we have shown all season”.
– Pellegrini returns to Real –
For outgoing Manchester City boss Manuel Pellegrini, the semi-final will be a return to the club he managed in 2009-10.
City’s only games against Real, unbeaten in their last eight games against English clubs and in the semi-finals for a record sixth successive time, were in the 2012-13 group stage. They drew 1-1 at home and lost 3-2 away.
City’s sporting director Txiki Begiristain said: “It’s a great tie against the team that has won the competition the most times.
“But we have got this far and we want to keep dreaming.”
Begiristain added: “They have shown that in the second leg at the Bernabeu they can be unstoppable.
“We need to be solid defensively, as we have been in the Champions League recently against Dinamo Kiev and PSG.
“Clearly they (Real) are (favourites), this is their 26th semi-final, their sixth in a row, but we are very capable. PSG are having a great season and we were able to knock them out.
“We are optimistic, but I repeat the key is solidity.”
Emilio Butragueno, Real’s director of institutional relations, said City would be very motivated given they had never made the last-four before.
“In the semi-finals any opponent will be a great team and we are speaking about players of the highest quality that can settle a game themselves in (David) Silva, (Kevin) De Bruyne and (Sergio) Aguero,” Butragueno told BeIN Sports Spain.
“We need to play two games at a very high level if we want to get to the final in Milan.”
Asked whether it was the best draw possible for Real, Butragueno said: “I remember being here exactly a year ago and everyone said afterwards we had been very lucky to avoud Bayern and Barca, but Juventus ended up eliminating us.
“The two games will be very evenly balanced. We can think playing at the Bernabeu gives us a certain advantage. But this is our sixth consecutive semi-final and in the five previous to this we have played away first three times and never made it to the final.”
The first leg of the semi-finals will be played on April 26-27, with the second leg scheduled for May 3-4. The final will take place at Milan’s San Siro stadium on May 28.