Former loanee congratulated Middlesbrough on their win.
The Belgian forward was on loan at Middlesbrough from Genk last season.
Middlesbrough, Sheffield Wednesday and Celtic were all reportedly interested in Jelle Vossen, who is now set to join Burnley.
Vossen has been linked with Burnley, Celtic and Sheffield Wednesday.
The Belgian now looks set to join Burnley this summer.
KRC Genk striker Jelle Vossen has been linked with Celtic, Sheffield Wednesday, Middlesbrough and Burnley.
Celtic fell at the play-off stage last year and will be looking to go one better this time around.
Burnley are hoping to sign the Belgian striker, also wanted by Celtic and Sheffield Wednesday.
Jelle Vossen is considering an offer to leave Genk this summer.
Middlesbrough, Sheffield Wednesday and Celtic are all reportedly interested in Jelle Vossen.