Best will receive the Christy Heffernan Memorial Trophy which was launched in 1999 by Kev Monks, to remember former Coventry City Supporters Club Irish Branch Secretary and the Chairman of the now merged with the Sky Blue Trust's Association of Coventry City Supporters Clubs And Groups.
Chris Coleman said: "Leon has most of the attributes you need to be successful - pace, strength and power.It is easy to forget that he is only 21 years old.
"He has worked hard all season and I have been impressed with him since I arrived. Having dscussed it with my staff, I believe Leon is a worthy winner of award."
Said Kev Monks, who organises the vote and has paid for the trophy for this year and most of the previous ten years: "Christy was always asking me how the young players and those in the reserves and youth team were getting on and I felt that this award for players aged Under 21 on the opening day of the season would make a fitting tribute to him.
"I'm sure he would have been highly delighted that this year's winner is a Republic Of Ireland U21 international!. Like Chris Coleman, I feel that Leon is a worthy winner."