Guus Hiddink and Louis van Gaal are two very different characters with a long rivalry that has seen them do battle in the Netherlands, Spain and England. Wesley Sneijder— who has played under both—described Van Gaal as the "tough school teacher" and Hiddink as "the friendly uncle," per Sky Sports.
Simon Kuper of ESPN FC wrote in December 2015:
...the last two relics of the legendary Dutch Seventies still working in top-class soccer have never got on. The boastful, humourless Van Gaal irritates Hiddink. Van Gaal, for his part, considered Hiddink a pragmatic, unadventurous coach.