|Rhythm matching is a learned skill. Early in a violinist's career he should be able to match rhythms from songs he hears. Even later in his career, when counting beats has become second nature, a musician will hear a teacher say that he has to "feel that rhythm."
My best friend growing up was a cellist. We were playing in the pit orchestra for the musical Kiss Me Kate, and we came to the piece Too Darn Hot! Poor David tried so hard to count the rhythm, but was completely unsuccessful. Then our teacher told him to be quiet, listen and feel what was happening. That's all it took.
Practice listening to music and matching simple and complex rhythms.
Dave Brubeck's Take Five is so easy to feel but a real trouble to count.