Just days after filing for a divorce from her estranged husband Lamar Odom, Khloe Kardashian was rumored to be seeing pro-baseball player Matt Kemp. However, according to inside sources, Odom believes that Kardashian and Kemp were secretly seeing each other before they officially split.

Rumors that the reality personality was dating the Los Angeles Dodgers player emerged after he posted an Instagram photo of the Jenner Christmas tree from inside the family's mansion on Dec. 12. He captioned the photo, "Best time of the year!! It's gonna b a Cali Christmas this year."

The following day, the two were spotted heading to the gym, driving in separate cars, the New York Daily News reported. Kardashian and the MLB star were also together in the VIP section at a series of concerts, including the Drake concert on Nov. 25, John Legend's concert on Dec. 1 and a Jay Z concert in L.A. on Dec. 9.

However, Odom believes that Kardashian and Kemp's relationship began long before she filed for divorce last Friday to end their four year marriage.

"Lamar feels betrayed because Khloe was telling him she wanted to save the marriage and he was really trying to do so," a source revealed to Radar Online. "He was far from the perfect husband, but Lamar genuinely thought there was a chance to save the relationship."

The insider continued saying, "Khloe always told Lamar she was only friends with Matt, but friends have been telling him that she had been hooking up with Kemp for months."  

However, another source close to 29-year-old Kardashian-Odom insists that she has never been unfaithful to the 34-year-old basketball player.

"Not true!!! She absolutely was not [cheating]," the source tells HollywoodLife.com.

Kardashian and Kemp have been friends for a while and he has shown her support through this difficult time. However, she doesn't want to rush into a relationship with him, sources said. 

"The main thing now is that they're friends and they're both not trying to begin anything romantic so soon," a source said, adding that "Khloe's still sad over her marriage to Lamar and is in a lot of pain."