The Reds have sold club captain Angus MacDonald to Hull City for an undisclosed fee. The 25-year-old has agreed a two and a half year deal at the KCOM Stadium.
MacDonald arrived at Oakwell from Torquay United in August 2016, and went on to enjoy a successful season at the heart of the Reds defence alongside Marc Roberts.
He was appointed as club captain in the summer after the departure of Roberts, when he joined Birmingham City.
However, he has struggled to cement a place in Paul Heckingbottom's first team this term, with injury and illness and the emergence of Liam Lindsay and Ethan Pinnock limiting his action.
He made 50 appearances for the Reds, and scored two goals, including a memorable last minute equaliser against Sheffield Wednesday at Oakwell in April 2017.
Also leaving Oakwell today, if only temporarily, is youngster Dylan Mottley-Henry who has joined League Two side Chesterfield on loan until the end of the season.
The 20-year-old, who only last week signed a new deal at Oakwell, spent the first half of this season on loan at National League side Tranmere Rovers.