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In fact, sending Mourinho off the team was a big risk because he was a very experienced coach. He won the conference league and made Rome a finalist in the European league. That's why Roma made a risky choice and appointed De Rossi as the head of the team. It seems that this change was appropriate and Rome is doing very well this year.
But the question is, how long will De Rossi be successful in managing Roma like now? Maybe for some time, Roma has been quite successful, but it cannot be confirmed whether Roma will be able to continue to survive as they are now under De Rossi's command. Mourinho is a competent coach, so he has many fans who really regrets the decision taken by Roma management to fire Mourinho
Danielle de Rossi was a great player and a Roma and football legend that has 16 years career. He knows the club more anyone else, and understand tactics and management. Appointing a new coach is always a risky decision, regardless his managerial experience. I don't think De Rossi a bad appointment, even he is inexperience. There are many example of inexperience coach became successful straight away in his first club, currently Xabi Alonso.
Throwing question about De Rossi's capability sounds bizarre after what he has been doing impressively at the club. It's not impossible that De Rossi become a successful coach with Roma if he continues to lead the team. There is no guarantee that Roma can be better with experienced coach next season.