By his usual high standards many would argue Mourinho is now in charge of a modest European club at AS Roma.
The Portuguese has tasted success at the very highest level, including winning the UEFA Champions League twice with FC Porto and Inter Milan.
He has also won the Europa League twice and last season completed a clean sweep of European trophies by guiding Roma to win the inaugural Europa Conference League trophy.
Mourinho's list of achievements include league titles in Portugal, England, Italy and Spain.
One of Mourinho's Champions League triumphs came in a treble-winning season with Inter Milan in 2010, with Sneijder a key cog of that side.
The former Netherlands midfielder has paid tribute to Mourinho on his big day and has backed the former Chelsea boss to take Roma back among the elite of Italian football.
"I have great memories of him, especially when we won the Champions League. He was very determined and so confident we would win that match," Sneijder told Stats Perform.
"He knows exactly how to behave with his players on the pitch but especially off it. As I said before, with him there was no need for a chairman, he protected all the players.
"For me, he is still number one."
"Of course, he is doing well there. As you said, Milan, Inter and Juventus with all their problems are a bit in trouble now, so this is the right moment [for Roma]," he added.
"But there is Napoli now who are doing great in Serie A and in the Champions League. It will be hard to beat Napoli, but Roma can beat all the others."
