The new issue of Us Weekly reports that Kate Hudson and Cameron Diaz are locked in a bitter battle over Alex Rodriguez. (On May 2, Diaz was spotted leaving A-Rod's $30,000-a-month penthouse with overnight bags; Hudson dated the Yankees slugger from May to December of last year.)
PHOTOS: Undercover lovers!
An insider believes Diaz is bedding Rodriguez as a form of retaliation after Hudson hooked up with Justin Timberlake in January 2007 -- just two days after the couple of four years split.
"Kate thinks it's payback, pure and simple," the insider says. And Hudson's not 100 percent wrong. Says a Diaz pal, "Cameron was actually in a serious long-term relationship with Justin. She thinks it's a joke Kate would be mad. Kate is only upset because she hates being single."
PHOTOS: Shocking star splits
In an effort to hold on to Rodriguez, one source even contends that Hudson (who has a son, Ryder, 6, with ex-hubby Chris Robinson) got breast implants postsplit to appeal to the Yankee's preference for "busty women."
PHOTOS: How Kate has flaunted her new boobs
For more details about Hudson and Diaz's fiery feud -- including their fight for the same roles ("Kate thinks Cameron is an aging old lady actress struggling to remain sexy and relevant," a source says), how Kate gets "crazy jealous" of the men she dates and why A-Rod reminds Cameron of her dad, pick up the new issue of Us Weekly, on stands now.