PUEBLO, Colo. ― Earlier today PBR.com confirmed that 20 days ago Valdiron de Oliveria had back surgery for a herniated disc.

The procedure took place in Rio Preto, Brazil, which is the same city where the PBR Brazil headquarters is located.

Oliveira is not expected to recover in time to compete at the season-opening Built Ford Tough Series event in New York and likely will miss all of January before returning to competition. The decision to wait until December could cost the six-year veteran a chance at contending for the 2013 title.

Oliveira, who was vying for his first world title in 2012, was hampered by injuries down the stretch. Late in the season, he tore a tendon in his riding wrist.

However, the fact that he was experiencing back spasms proved more significant and the 33-year-old veteran had a stretch of three consecutive events ― Tampa, Fla.; Greensboro, N.C., and Philadelphia ― in which he was unable to attempt two bulls on the opening night of the events.

While most analysts and observers focused on his wrist injury and, perhaps, the mental stress of having lost his lead atop the world standings for the second year in a row at the BFTS event in Thackerville, Okla., only later was it learned that Oliveira had suffered a herniated disc.

He was originally expected to have the problem addressed in Dallas following the World Finals.

Oliveira's decision to have the procedure in Brazil was first discovered earlier this week when his neighbor in Decatur, Texas, talked with J.W. Hart and told the former bull rider-turned CBS Sports Network broadcaster that he was looking after Oliveira's house while he recovers from the surgery.

Oliveira, who was ranked No. 1 in the world for majority of the season, finished 2012 ranked fourth in the world.

He will turn 34 years old in June.

This story will be updated as more information becomes available.

Follow Keith Ryan Cartwright on Twitter @PBR_KRC.