HITC Sport understands from sources close to the club that Sunderland are closing in on Celtic defender Adam Matthews, with the Welshman undergoing a medical on Friday at the Stadium of Light.
Celtic accepted a bid in the region of £2million for Matthews earlier this week and the player has been given the green light to travel to Wearside for talks and a medical.
Matthews has spent the last four years at Celtic after joining the club in 2011 from Cardiff City.
The 23-year-old was a regular in Ronny Deila's side last season, making 48 appearances as Celtic won the Scottish Premiership title and Scottish League Cup.
Celtic have reluctantly agreed to let Matthews go after bringing in a readymade replacement in Saidy Janko from Manchester United.
If Matthews agrees personal terms and passes his medical with the Black Cats, he will become Dick Advocaat's second signing of the summer following the arrival of Sebastian Coates from Liverpool.