The Brazilian, whose current contract with Adelaide ends in June, has drawn interest from other A-League teams and clubs in Asia.

But at this stage United haven't been as forthcoming.

Diego says his preference is to stay in South Australia and would like to hear what his current club could offer.

"To me it's a disappointment because they know I could sign with other clubs and they still haven't approached me," he said.

"It's disappointing because I feel like I've done enough to earn a contract. Even if they don't want to give me a lot of money they could say: 'Listen, this is what we have for you, if you want to stay this is what we want'.

"I know it's difficult for a coach to choose his players and if he's not happy with me I'm sure there's going to be other clubs."

A stumbling block for the Reds could be Diego's need for financial security in the coming years. The 28-year-old admits dollars and cents will be a major factor in his final decision.

"I think it would be more about the money and maybe the lifestyle," he said.

"For players that are younger, I think they may be looking to go to Europe, that's where the best teams are, that's where the best players are and that's where the money is.

"I never got to play in Europe but there's a good market in Asia with good money out there in Korea, China and Japan."

Diego said overseas clubs are required to wait until January 1 before officially approaching him with offers. While he's open to the opportunity of playing in Asia, he's not overly optimistic about his chances.

"Obviously the (Asian Champions League) grand final didn't help my cause, or any other players, because it was a poor performance by the whole team but I've heard a couple of things but there's nothing on paper yet," he said.