Coventry City will face a trip to Millwall next season after they were beaten in the League One Play-Off Final at Wembley by Barnsley 3-1
Barnsley were ahead after less than two minutes when Fletcher was allowed to get through and drill home.
In the 18th minute, the Tykes had a second thanks to a stunning strike from Adam Hamiill.
Millwall came back with a 34th minute shot on the turn from Adam Beevers to see Barnsley lead 2-1 at the break.
A crowd of 51,277 saw Barnsley go 3-1 up through Isgrove, which sparked some trouble in the top tier of the stand.