Jose Mourinho has praised Lionel Messi for helping him to evolve as a coach, despite never managing the Barcelona superstar.
The 'Special One' has managed the likes of Chelsea, Inter Milan and Real Madrid when he came up against the 32-year-old Argentine forward.
And the ex-Manchester United boss said the experience of playing against Messi made his pre-match preparations even more important.
"I always say that I owe so much to my players, and to those who haven't been my players but those who created problems for me," he told EFE.
"For example, Messi never played for my team, but he played against me and he has made me a better coach for having to prepare matches [to stop him].
"When I say Messi, I also mean the other great players I've faced."
Mourinho's scouting report on Barcelona in the 2005-06 season emerged online back in March, which spotlighted his attention to detail on Messi at the time.
But the Portuguese manager also revealed how far he came against the Barcelona captain when he revealed his tactics against the Spanish side in the Champions League semi-finals in 2010.
The Argentina international has missed the start of Barcelona's new season due to a calf injury he picked up in pre-season.
And Barcelona boss Ernesto Valverde said on Friday that the five-time Ballon d'Or winner could be a doubt for their Champions League clash with Borussia Dortmund on Tuesday.
"I am not a doctor but it seems that the scar was opened a little and that made us more cautious," he said.
"In terms of him being able to return, I don't know if it will be Tuesday or maybe later.
"I don't want to say anything to lower expectations, but I find it difficult for Tuesday."
Barcelona defeated Valencia 5-2 at the Camp Nou on Saturday and are fifth in La Liga.
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