Marnick is a full back, capable of playing on either side, who joined Manchester United from Standard Liege in the summer 2010. Renowned for his consistent level of performances, Marnick was rewarded with his debut for Manchester United in the 2012/13 League Cup.
Marnick started the 2013/14 season with Manchester United's Under-21 side but joined N.E.C. Nijmegen on loan in September for the rest of the season.
Two years after his debut, Vermijl was back in the Manchester United first team as he started in the 2014/15 League Cup 2nd Round defeat away to MK Dons.
Marnick signed a 3 and a half year contract with Sheffield Wednesday on 2nd February 2015.