Arsenal boss Unai Emery labelled Manchester City counterpart Pep Guardiola as the best manager in the world.
Emery will go head-to-head with Guardiola when Arsenal visit Premier League champions City on Sunday, having never beaten his countryman.
Former Valencia and Sevilla head coach Emery suffered a 2-0 home defeat to Guardiola's City in the pair's last clash in August.
And Emery heaped praise on Guardiola, who has delivered silverware at City, Bayern Munich and Barcelona in an illustrious career.
"I have analysed a lot of teams and coaches and I think it's difficult to find one coach who is better than Guardiola," Emery said.
"His career is a very big career. We started together. He started with the Barcelona second team, I started with Lorca and Almeria [In Spain's third and second tiers].
"I learned a lot looking at his team — it's good to look at each other when we are coaches to learn different things between us. I think in his career he's doing the best in all the coaches in the world.
"He has had the possibility to take the best players at Barcelona, in Bayern and in City, little by little. He is, every year, improving with great players and also paying a lot for some players. But he led them, at Barcelona, Bayern and City, one step more every place."
Arsenal are fourth in the Premier League, nine points adrift of second-placed City, who are five points behind leaders Liverpool after 24 matches.
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