Zenden retaining Chelsea hope
The former Barcelona winger joined The Teessiders on a 12-month loan deal to play first team football after being surplus to requirements at Stamford Bridge.
Zenden has enjoyed his spell at The Riverside Stadium but is backing his ability to succeed with The Blues at a higher level.
However, the fleet-footed Dutchman hinted he would be willing to stay with Steve McClaren's side, but the decision is out of his hands.
"I have never given up hope of returning to Chelsea," said the Dutchman. "The paperwork says I'll be a Chelsea player again so I have to think about going back.
"I want to play at the highest level. It's good Middlesbrough are in the Uefa Cup, but it's probable Chelsea will play in the Champions League.
"We have won the Carling Cup, but I'm owned by Chelsea so it's not all up to me."