The Croatian joined the Blues from Inter Zapresic in 2009 but has never made a first-team appearance, instead being farmed out on loan 10 times.
Indeed, Delac - who became Chelsea's longest-serving player following John Terry's departure in 2017 - has never officially been registered by the Premier League club due to work permit issues.
The 25-year-old is out of contract in June and, according to The Sun on Sunday, he is already on the hunt for a new team on a permanent contract.
Delac, who was born in Bosnia and Herzegovina, stated in November last year that Chelsea had faith in him, but work permits were the biggest stumbling block during his time in West London.
Belgian club Mouscron last took Delac on loan during the 2016-17 season.