The 32-year-old is out of contract at the Championship club at the end of the season according to Transfermarkt.co.uk, and no new deal is in place.
The former Blackpool star has been injured for the past three years with a serious knee problem which he suffered during a collision with a teammate - goalkeeper Frankie Fielding, now at Bristol City - in a derby game against Nottingham Forest in March 2012.
Barker will be at the iPro Stadium today for Derby’s Championship encounter against Reading, and he is looking forward to showing his appreciation to the fans.
Whatever happens in the future, it'll be nice to thank you today + show my appreciation for all your support over the last few years! #dcfc— Shaun Barker (@barks5) May 2, 2015
Derby are currently sixth in the Championship table with 77 points from 45 matches, two points clear of seventh-placed Brentford.
If the Rams pick up all three points against Reading today, then they will secure a playoff spot irrespective of results elsewhere.