Following the conclusion of the 2013 Varsity Cup, Willemse was called up to Western Province’s Vodacom Cup squad where he made his first team debut against Argentinian side Pampas XV.
Willemse made his Currie Cup debut during the same campaign as he came off the bench against the Sharks. The hooker was named in the Stormers Super Rugby squad for the 2014/15 season.
The Cape Town native joined Southern Kings in 2017 and made 36 total appearances for the Port Elizabeth outfit, scoring five tries, before joining Edinburgh.
Willemse spent two seasons with Edinburgh in the Pro14 before making his move over to London Irish.
The hooker has represented South Africa at under-20 level, where he scored two tries in three appearances at the 2013 IRB Junior World Championship held in France.