The 32-year-old joined Sporting Lisbon on a free transfer last summer, but the former Hoffenheim keeper has failed to become a first-team regular for the Portuguese side.
He told Kicker: “Looking back at how things have progressed for me in my career, I have to admit I should never have left Stuttgart.”
Hildebrand added: “I now have an opportunity to have a good future.
“I would like to be back in the Bundesliga and I believe I have got a chance to win myself a place in the league in the coming weeks.”
