Mertens makes his first start of the tournament after coming on as a substitute in all three of Belgium's group matches and will feature on the right flank instead of the disappointing Carrasco, completing a fearsome attacking unit containing Kevin De Bruyne, Eden Hazard and Romelu Lukaku.
Radja Nainggolan retains his spot in midfield alongside Axel Witsel following Mousa Dembele's ankle injury suffered against Ireland, while Thomas Meunier remains at right back.
For Hungary, talented youngster Adam Nagy and playmaker Laszlo Kleinheisler return after being rested against Portugal, with the former set to work alongside 37-year-old Zoltan Gera in hoping to silence key man De Bruyne.
Adam Lang continues to deputise for Attila Fiola at right back with the latter sidelined with an ankle injury, while Tamas Kadar returns at left back and Gergo Lovrencsics retains his place after a lively showing against Portugal.