Pep Guardiola has warned Real Madrid that they should not become "complacent" after winning the La Liga and Champions League double.
On Saturday night, Real strengthened their dominance in Europe by becoming the first team to successfully defend the Champions League, but Guardiola has backed his former side Barcelona to hit back next season.
Between 2008 and 2012, he led the Catalan giants to three league titles and two Champions League crowns, and he has insisted that Real have some way to go before eclipsing the achievements of their fierce rivals.
The 46-year-old told Sport: "No-one has done what these players have done in the last 15 years. It is the most competitive team of the last 15 or 20 years. Competitiveness is to win every week and what these players have done in the league in the last fifteen years no-one has achieved.
"In Europe, a bad game can knock you out - the Champions League is a shorter competition - but the league is getting up and performing every day and they have done it for years. There is no better team in the world. They will do it again.
"I congratulate Real Madrid, but they should not be complacent. Barca always returns."
Guardiola is now at Manchester City, and will hope to challenge both clubs in Europe next season after making significant additions to his squad at the Etihad Stadium.
