 Rihanna then sings the opening lines, "Baby, baby, when we first met, I never felt something so strong".Critics noted similarities among the structures of "Rehab" and some of Timberlake's songs, such as "What Goes Around... Comes Around" and "Cry Me a River".Spence D. of IGN wrote that the song has an "R&B swoon", similar to Rihanna's previous singles.