The 23-year-old Cameroonian was moulded in Barcelona’s academy, where he spent five years, before switching camp to the Dutch giants in 2015.
Onana was one of Ajax Amsterdam’s success stories last season as they made it all the way to the semi-finals of the UEFA Champions League, lifted the Dutch Cup and won the Eredivisie title as well.
Onana penned improved terms at Ajax in March, but he still has lingering doubts about his long-term future at the Johan Cruyff Arena and has welcomed a potential return to the Camp Nou.
"I don't know what will happen next year, if I will stay or not," he told Marca ahead of a return to Spain when Ajax face Valencia in the Champions League on Wednesday.
"I never imagined I would play in a Europa League final or Champions League semi-finals. When I left Barcelona, my idea was to be the third goalkeeper of a top-level team and then have the opportunity to get into a professional team, to learn from the biggest, and Ajax gave me that opportunity.
"I want to be the best goalkeeper in the world. It's the dream I have and, as they say, dreaming is not forbidden.
"[Barcelona] have always been my club. They gave me everything. It was the road to get into Europe and I'm very grateful.
"If they loved me again, I'd be delighted, but you never know."
