Former MLB star Jose Canseco took to twitter last night with accusations that Alex Rodriguez has been cheating on his fiancee, Jennifer Lopez, with Canseco's ex-wife, Jessica.

A-Rod proposed to JLo during a recent trip to the Bahamas, a little over two years since they started dating. However, Canseco says Lopez "has no idea who he really is."

In a series of tweets posted late Sunday night, Canseco claims:

"Watching World of Dance watching J.Lo text Alex Rodriguez little does she know that he is cheating on her with my ex-wife Jessica poor girl she has no idea who he really is"

"I was there a few months back with her when he called her on her phone."

"Alex Rodriguez stop being a piece of shit stop cheating on Jennifer Lopez"

(Photo by Jon Kopaloff/WireImage)

Additionally, Canseco challenged Rodriguez to a fight and says he's willing to take a polygraph test as proof that he's not lying.

"Alex Rodriguez I challenge you to a boxing match or an MMA match anytime you want"

This isn't the first time that Canseco looked to damage A-Rod's reputation. In his 2008 book, “Vindicated,” Canseco claimed to have introduced Rodriguez to his steroid supplier and mentioned that the Yankees Slugger was interested in his now ex-wife Jessica during the late 1990s.