Mary J. Blige and Janet Jackson got rehearsals for the 2006 Billboard Music Awards off to a rousing start Saturday (Dec. 2) at the MGM Grand Garden Arena in Las Vegas. Blige nailed her vocals for a medley of two songs from her smash hit album "The Breakthrough" on the first take, while Jackson painstakingly went over choreography for her numbers that will open the show on Monday.

Looking stylish in a brown cable-knit turtleneck, sunglasses, gold hoop earrings and baggy grey pants tucked into her boots, Blige was in remarkably clear voice right from the get go. Later in the evening, Jackson first taped a performance featuring two classic tracks that will begin streaming tonight on American Express' Web site, then proceeded to run through her effects-heavy medley for the Fox BBMA telecast.

In other BBMA news, Stevie Wonder has stepped in for an ailing Celine Dion to present Tony Bennett with the Century Award, Billboard's highest honor for creative achievement. Bow Wow and Def Leppard's Joe Elliott and Phil Collen have also joined the list of presenters.

Today, the Fray, Fergie, the Killers, Gwen Stefani and Ludacris with Pharrell and Young Jeezy will rehearse for the BBMA performances. As previously reported, Nickelback, Rascal Flatts, T.I. and Blige lead the field of award finalists with five each.