Matt Kemp was NOT single when he started dating Rihanna. Or at least that’s what R&B singer LeToya Luckett thought.

Matt and LeToya had been dating for about 6 months.  “They were trying to keep it quiet because they didn’t want anyone in their business, but [Letoya] really liked him.”

And LeToya was SHOCKED when she learned, that Matt had started dating Rihanna. The insider tells, “We read the rumors  about Matt and Rihanna, We didn’t believe it . . but when we saw the photos it was like pow . . . yup, he’s seeing [Rihanna].”

We hear that LeToya is still very hurt about the whole situation. They tell, “LeToya liked him, she’ll get over it, but right now she’s hurt.”