Transfer gossip: Sunderland, Middlesbrough and Celtic linked with Championship striker - reports

Football Insider have stated that Celtic, Middlesbrough and Sunderland are tracking the 24-year-old attacker ahead of a summer move. The Black Cats will be in the market for a striker after injuries to Ross Stewart and the return of loanee Ellis Simms to Everton leaving Tony Mowbray short of options post-January.

The former Wales youth international has found himself in good form in recent weeks, scoring three in his last seven taking his total for the season so far to eight goals in 13 starts.

Cullen, who came through the ranks at Swansea City’s academy, is about to enter the last year of his contract with Sunderland set to lose attackers Amad Diallo and Joe Gelhardt back to their parent clubs Manchester United and Leeds United when their loans come to an end at the end of the season.