(CNN) -- Cristiano Ronaldo has consistently been linked with a move back to Manchester United -- but Real Madrid star Mesut Ozil insists his club must hold onto the player if it is to challenge at the very top. 

Ronaldo, who left United for Real in a world record $130 million deal in 2009, has been the subject of much speculation in recent months. 

The 28-year-old has scored 201 goals in 199 appearances for Real and club president Florentino Perez recently stated that he expected Ronaldo to finish his career in the Spanish capital. 

But the speculation refuses to disappear -- leaving Ozil hoping his Portuguese teammate stays put. 

"Cristiano Ronaldo is very important to the team, just look at all the goals he has scored in the past few seasons," he told CNN. 

"He's a great person off the field. I hope he can stay here for a long time because he can help us win important titles." 

The loss of Ronaldo would be a huge blow to a Real side hoping to snatch the league title back from Barcelona and win its first Champions League crown since 2002. 

Real has lost out at the semifinal stage in each of the past three seasons with Borussia Dortmund the last team to put paid to the Spanish club's dream of a 10th triumph in the competition. 

"We have come very close to winning the Champions League in the past few years and that leaves a very bitter taste in the mouth," Ozil revealed. 
How many seasons?
three seasons