Alan McCormack will leave Brentford when his contract comes to an end at the end of the season.
The Irish midfielder joined the Bees in 2013 from Swindon after both sides missed out on promotion through the League One play-offs.
He quickly became a fans' favourite with his no nonsense style and moved to right back after Shaleum Logan fell out of favour under Uwe Rosler.
He kept his spot there and helped the Bees win promotion as League One runners up.
McCormack started the Championship season at right back but a serious injury at Bolton ended his campaign.
Last season saw the Irishman have spells in and out of the side with injuries but he played enough games to trigger a contract extension.
This year, McCormack has only made 10 Championship appearances, just two of them from the start, as injuries took their toll again.
Head coach Dean Smith told the club's official website: “I would like to thank Alan for all his efforts while he has been at Brentford.
"Alan has suffered with injuries since I have been here but has played his part in a period of success for the club over the past four years. I wish him all the best for the future.”
In total, the 33-year-old has played 103 times for the Bees and has scored on three occasions.