Belgium international Hazard's contract at Stamford Bridge expires in 2020 and he has been repeatedly linked to Madrid, rumours he has refused to be drawn on.
Former Chelsea forward Gudjohnsen left Chelsea for Barcelona in 2006 so knows all about the lure of Spain's big clubs, yet he believes winning this year's Europa League, and consequently qualifying for the Champions League, could be a factor in Hazard's decision.
Maurizio Sarri's side are in the quarter-finals of the competition and faced Slavia Prague in the first leg.
Gudjohnsen, who was speaking on the UEFA Europa League Trophy Tour driven by Kia, told Omnisport: "It's difficult and dependent on your situation - dependent on what your desires and your dreams are.I don't know Eden Hazard personally, he's always spoken very fondly of Chelsea and how happy he is there".