Douglas started his career with Premier League side Blackburn Rovers
Swindon Town captain Jonathan Douglas has informed the club he is leaving, with Brentford his likely destination.
Douglas, 29, joined the Robins from Leeds in 2009 and made 84 league appearances in his two seasons.
"He rang me to say he'd had an offer from Brentford," chairman Jeremy Wray told BBC Wiltshire.
"In truth League Two does not appeal to everyone and from his perspective if he has the opportunity to play at a higher level then I can understand that."
Wray continued: "I appreciated him calling me personally, I respect his honesty and I wish him well.
"In a way it feels like unfinished business. He was our player of the season in 2010/11 but he was disappointing by his standards last season.
"But on another level I think it's important to have a clean slate after what happened last season [Swindon's League One relegation]."
Meanwhile, striker Leon Knight, midfielder Ibrahim Atiku and defender Oliver Risser have all joined on trial.
Knight, 28, has played for Huddersfield, Brighton and Swansea in a career that has also taken in spells in Greece and Northern Ireland.
Ghanaian Atiku has played in Greece, Israel and Sweden and had a trial with
Inverness in Scotland in 2008.
Risser has had spells in Germany, Iceland and Norway and plays international football for Namibia.