Borussia Dortmund centre-back Neven Subotic says he will give "100 percent" to recover his fitness after a rib injury ended his hopes of a summer transfer.
Subotic, 27, had decided to leave Dortmund after falling down the pecking order under Thomas Tuchel, but a move to Premier League side Middlesbrough collapsed when he failed a medical on Wednesday.
Dortmund said it is likely the defender, who missed the final weeks of last season with a thrombosis in his arm, will be out until the end of 2016 with the unspecified rib issue and added in a statement: "There will be no transfer involving the defender during this period."
The Serb, who joined Dortmund from Mainz in 2008, spoke of his frustration in a statement on Facebook but said he was determined to battle back to full fitness.
"It's hard on me because I was looking forward to a new season on the pitch like a small boy who can finally live his dream again," Subotic wrote. "What remains is my dream. A lot of hard work lies ahead of me. Like always, I will give 100 percent to return to full fitness and step on the gas where I am needed."
Subotic, who said he had believed he was fit again following the thrombosis issue, added: "I wanted a challenge that I can actively work on. I now have it, but sadly it's not on the pitch."