Derk Boerrigter spent three years at Celtic until being paid off in 2016.
Derk Boerrigter endured a torrid time at Celtic.
The Dutchman had an injury prone time at Celtic but appears to be in good spirits.
Middlesbrough may cut their losses on one-time Ajax wonderkid Viktor Fischer - but Celtic could offer him an opportunity to live up to expectations.
The Dutchman failed to have a lasting impact with the Bhoys.
The Dutchman's Celtic Park contract was terminated in April.
The Dutchman is keen on a move to the United States.
Celtic winger Derk Boerrigter is set to leave the club.
The Dutchman has struggled in Glasgow.
Andy Walker believes Celtic's recruitment has been poor in recent years.