Benitez believes they were close to building a title winning team.
"We had the confidence we could win the league but you have to wheel and deal. You cannot bring in two or three top-class players if you don't have the money. You have to sell. We sold Xabi Alonso and bought Glen Johnson, Alberto Aquilani and Sotirios Kyrgiakos. We [should have] had money but I couldn't use it because we had to meet the interest payments," he told the Mail on Sunday.
"We had one top-class player who was our target, Fiorentina's Stevan Jovetic. As far as I was concerned, we had the money for him in our budget. But then the owners said: 'No, no, we don't have the money'. Then he scored against us in the Champions League to help knock us out!
"If you have your budget and you know that is happening, fine. But my budget was always given to me as a net figure [after taxes] for wage negotiation. But in the last year it was gross - a massive difference - but I didn't know. No one told me it had changed."