Smit, a right-handed player, featured most successfully in the doubles format, in which he reached 121 in the world.

[1] All of his eight main draw doubles appearances on the ATP Tour were with countryman Martijn van Haasteren and included two quarter-finals.

The pair reached the quarter-finals at the Dutch Open Amersfoort in 2007 by upsetting second seeds Tomas Behrend and Christopher Kas, then in 2008 they were quarter-finalists at the Zagreb Indoors.

As a singles player he appeared in his only ATP Tour main draw at the 2006 Kingfisher Airlines Tennis Open in Mumbai, for a first round loss to Gouichi Motomura.

In 2010 he won a match over then world number 62 Pablo Cuevas on clay at the Scheveningen Challenger.