Britt Assombalonga is due for a medical at Middlesbrough after Nottingham Forest accepted a bid worth up to £14million for the striker.
Burnley have also been interested in the 24-year-old but were reluctant to go as high as Garry Monk’s side, who have been trying to negotiate a fee for a number of weeks.
Mark Warburton did not wish to lose his top scorer but it is understood a £15m release clause, written into the five-year contract penned last summer, weakened the club's position.
Forest would have preferred to lose Assombalonga to a Premier League team but Monk has been backed significantly by chairman Steve Gibson during this transfer window.