Baseball star Matt Kemp, 30, is expecting his first child with stylist girlfriend Nchimunya Wulf, 35, after keeping their relationship on the down-low for the past year, X17online can report exclusively.

Kemp previously dated Rihanna and Khloe Kardashian, but his days of being a player seem to be coming to an end! A source close to the expectant couple tells X17online exclusively:
    "They've been living together for about a year and she's four months along. They've gone on a number of trips together, and she's even traveled with his family too. They may not be super public with their romance, but they're head over heels and thrilled to become parents."

Earlier this fall the two traveled to her home country of Zambia to work with the Chipakata Children's Academy Foundation, of which she is the Executive Director. Wulf recently returned to Chipakata, where she debuted her baby bump (see pic above). Our source tells us:
    "Nchimunya was born in Zambia and she grew up in Kenya and Congo, so it really meant a lot for her to get Matt so involved with her charity. She's also been on a handful of trips with his mother, Judy Henderson, so this isn't coming as a surprise to those close to the couple."

No official word from Kemp's camp, but seeing as Wulf is already showing, we have a feeling an announcement is imminent!

UPDATE! - Matt has Tweeted that he is NOT expecting a child with Wulf ... and we're bummed! Apologies to Matt -- our source checked out and many signs pointed to a baby on the way for the baseball hottie but alas, it wasn't meant to be. We can't wait for it to happen, though ... Khloe and Rihanna let a good one get away!