Erasmus left Orlando Pirates for French top-flight side Rennes a little less than a year ago but has struggled to break into the first team.
The 26-year-old has made just one start and nine substitute appearances for Christian Gourcuff’s side and last played in a 7-0 cup loss in mid-December.
Effectively Erasmus is sixth choice in the attacking positions with the likes of Giovanni Sio, Kamil Grosicki, Wesley Said, Pedro Henrique and Adama Diakhaby all higher on the minutes-played statistics.
Lens are second on the Ligue 2 table and gunning for promotion this season.
Erasmus will be delighted to get another opportunity to earn more game-time and show his talent in France.