The 20-year-old midfielder joined Northampton Town on loan from Brighton last summer and is scheduled to stay at the League Two club until the end of the season.
He has started nine of Northampton’s 12 League Two games and his performances have quickly made him a mainstay in their team.
Ahead of the transfer window opening in January, there is serious interest in him amongst clubs in the Championship.
And it has been claimed that Sunderland are one of the clubs who are interested in snapping up Leonard, having registered their interest.
Tony Mowbray remains committed to adding more players to his squad in the winter window following a solid start to the season.
Huddersfield Town and Preston North End are also amongst the clubs who have their eyes on the midfielder.
Brighton are now considering cutting short his stint at Northampton in January in favour of a Championship loan.
The Premier League club believe it could serve his development better if he spends the latter half of last season in the second tier of English football.
