Sir Alex Ferguson believes Wayne Rooney could have excelled "in any era" and has compared the Manchester United captain to club legend Sir Bobby Charlton.
Rooney's testimonial takes place on Wednesday night against his former club Everton, with United rewarding a player who has made 520 appearances since joining as an 18-year-old in 2004.
Ferguson, who managed Rooney for nine of his 12 seasons before retiring after United's last title-winning season in 2012/13, offered a glowing tribute to the striker who sits just four goals behind Charlton's all-time scoring record of 249 strikes for United.
Speaking to the official United programme, Ferguson said: "He [Rooney] was an exciting signing [in 2004]. It was fairly shortly after I'd got rid of the idea of retiring and changed my mind, and I had to rethink about how we were going to take the club forward.
"When you make the decision to retire, you stop thinking, but once I decided to stay I started thinking again and it was really centred around bringing energy back into the team by looking at young players.
"Of course there was Cristiano Ronaldo, then there was Rooney, and it was a fantastic period. The two of them were unbelievable.
"Wayne came in as a first-team player right away, even though he was only 18, and he's gone on to play for Manchester United for 12 years, which is very difficult in the present day.
"I always think that great players can play in any era. Bobby Charlton would have been a great player today and Wayne Rooney would have been a great player back then."
Rooney's public persona is quite reserved after 14 years in the spotlight as a player for Everton, United and England but he is well known to present a more fiery demeanour to his team-mates behind closed doors.
Louis van Gaal says he was very quickly struck by the respect Rooney's team-mates had for him at United and he had no hesitation in making him his captain.
Van Gaal, also in the testimonial programme, said: "I was very quickly convinced of his personality and that's why he was easy to work with. I quickly decided he would be my captain because I saw also the attitude of his fellow players towards him.
"They approached him always with a lot of respect and that's also important when you have to install a captain. It is very important that he is seen by his fellow players as a very important person in the dressing room, and there is no question that he is very important at United."
Rooney also drew praise from his newest manager Jose Mourinho, who called the 30-year-old's achievements "simply incredible".
The United boss said: "Wayne has provided many memorable goals and performances in his time here and I am sure he will provide many more memorable moments for United in the coming years."