Career
Early career
Clasie arrived at the youth Feyenoord Academy (Varkenoord) as a 9-year-old in the summer of 2000 and progressed through the ranks to the Feyenoord/Excelsior U19s. In the summer of 2010 the Harlem-born youngster went out on loan to Excelsior. Clasie made his professional debut for Excelsior on 15 August 2010, when he was part of the starting line-up in the Rotterdam derby victory against Feyenoord (3–2).
Feyenoord
Clasie was brought into the first-team squad at Feyenoord at the start of the 2011/2012 season and incoming coach Ronald Koeman immediately handed the youngster a place in the starting line-up.
On 31 July 2011 he made his debut for Feyenoord in a friendly game against Málaga. Because of his good play and his tenacity he soon became one of the most popular players among the supporters.
On 29 August 2014, a day after Clasie helped Feyenoord qualify for the group stage of the Union of European Football Associations Europa League, Clasie agreed to extend his contract until 2018. Clasie explained the decision that he was keen on developing himself as a player within the team as well as developing together with the team as a whole.
Southampton
However, on 15 July 2015, Clasie signed for Southampton on a five-year deal for a fee in the region of £8 million.
This meant he would once again link up with Ronald Koeman who brought him into the Feyenoord first-team In November 2010, two months after his debut for Excelsior, he was selected for the Netherlands U21 squad. In February 2012, Bert van Marwijk, the coach of the first team of the Netherlands, pronounced his interest in Clasie.
He was made aware that his name was on the stand-by list for Euro 2012.