Xabi Alonso will have a keen eye on this weekend's Manchester derby having worked first-hand with rivals Jose Mourinho and Pep Guardiola.
The managerial duo endured a testing relationship when in charge of Real Madrid and Barcelona, and the pair will renew rivalries when Mourinho's Manchester United host Guardiola's City at Old Trafford in the Premier League on Saturday.
Both men are regarded among the world's finest coaches, with Mourinho's pragmatic approach often in stark contrast to the possession-based game preferred by Guardiola.
Alonso is a man who knows the two well, having represented Mourinho at the Santiago Bernabeu, before playing under Guardiola at Bayern Munich.
And the midfielder is intrigued by their latest battle.
"It is a very big game in England. I think it will be a tactical match," he said. "Both coaches are methodical, they want to analyse everything. We'll see what will happen. I hope I can watch the game.
"I think they show many things in terms of personality and in terms of what kind of leaders they are. In terms of football they have their own ideas how to approach the game, the ambition they have, offensively, defensively.
"In those terms they are different. But for sure they are very competitive and they get the best from each player. For a player it is like a motivation to have a trainer that gets the best of you.
"I think they share many things in terms of personality and in terms of what kind of leaders they are."