(CNN) -- Legendary Brazilian footballer Pele believes Jose Mourinho's return to Chelsea will benefit the London club but he has warned there is no guarantee the Portuguese can deliver success.
Mourinho made his long-awaited return to Stamford Bridge on Monday, after cutting short a three-year tenure at Real Madrid despite having another three years left on his contract.
The 50-year-old won the 2012 league title with the Spanish giants, and the Copa del Rey the year before, but failed in the club's primary objective -- to win a 10th European crown.
The relative lack of success in the Champions League, where Mourinho guided Real to the semifinals in each of his three seasons, may underpin Pele's comments about his reappointment at the home of the 2012 European titleholders.
"Mourinho's return is good for Chelsea because he's a good coach," Pele told CNN's World Sport.
"He is talented and very honest. I know him personally. But football is a box of surprises.
"He has to have a bit of luck because in football, sometimes the best doesn't work. I wish him good luck."
During his first stint in charge of Chelsea from 2004-2007, Mourinho delivered the club's first English title in half a century before adding another Premier League crown, an FA Cup and two League Cups as well.
While he was away, the former Porto manager won his second Champions League with Inter Milan in 2010, a year when he won the league title for the second time with the Italian club.
Desperate to win the Champions League for the first time since 2002, Real Madrid turned to Mourinho just days after he ended Inter Milan's barren 35-year run in the competition.
But even with the goalscoring ability of star player Cristiano Ronaldo, the semis proved an insurmountable barrier as successive exits at the hands of Barcelona, Bayern Munich and Borussia Dortmund followed.
Mourinho's relationship with his compatriot Ronaldo broke down towards the end of his Madrid reign and the coach explained why in typically outspoken fashion during an interview broadcast by popular Spanish football show "Punto Pelota" on Tuesday.
"I had only one problem with him -- very simple, very basic -- which was when a coach criticizes a player from a tactical viewpoint, trying to improve what in my view could have been improved," he said.
"And at that moment he didn't take it very well because maybe he thinks he knows everything and the coach cannot help him to develop more."
While Ronaldo's future at Real Madrid has been the subject of recent debate, the endless speculation is finally over about where a Brazilian youngster who is often compared to Pele will end up.
Neymar, 21, signed a five-year deal with Real's great rivals Barcelona this week, leaving behind the very club where Pele made his name from 1956-1974: Santos.
After winning numerous titles with the club, including the 2011 Copa Libertadores, Neymar has often been labeled "the next Pele" but the man himself -- still the only player to have won the World Cup on three separate occasions -- refuses to make such a comparison.
"To be the new Pele would be very difficult, because my mother and my father closed the machine," joked the 72-year-old, who lifted the Jules Rimet trophy in 1958, 1962 and 1970.
"But no doubt he is one of the best players we have in Brazil."
"Of course in Brazil we have a lot of excellent players like Zico, Tostao, Rivelino, Pele, Ronaldinho, but the last two years we have Neymar, who is very talented.
"I hope he has luck in Barcelona. I didn't like it so much because he used to play in my team, Santos. I lost a good player. But it's important to understand that he deserves to go to the best team."