Jake Ellenberger has agreed to step in on short notice and face Sean Pierson at UFC 129 later this month.Rift Gold

The UFC confirmed the change late Wednesday night.

The opponent switch was necessary after Pierson's original opponent, RIFT Platinum Brian Foster, was forced to withdraw after a pre-fight MRI discovered a brain hemorrhage.

The 26-year-old Ellenberger (24-5) has proven himself to be one of the rising stars of the welterweight class, winning seven of his last eight fights, including three in a row. Last time out,rift gold he beat Carlos Eduardo Rocha in a close, split decision at UFC 126. The April 30 date gives him about two-and-a-half months in between fights, but only about two weeks to prepare.

Meanwhile, Pierson comes in riding a six-fight win streak. The Ontario native made his UFC debut last December, defeating Matt Riddle by unanimous decision.

UFC 129 should make him a home favorite. It takes place at Toronto's Rogers Centre. RIFT Platinum The event is headlined by a welterweight title match pitting Pierson's training partner Georges St. Pierre against challenger Jake Shields.

As for Foster, a burst blood vessel in his brain is expected to heal on its own rather than require surgery. For now, no timetable is set for his return.