Undefeated light heavyweight Thiago Silva (Pictures) has withdrawn from his Oct. 18 co-headlining bout against Lyoto Machida (Pictures) at UFC 89 “Bisping vs. Leben” in Birmingham, England.

An American Top Team representative confirmed a report from intheguard.tv, which said Silva sustained a back injury in training. The rep said the decision was made Thursday to pull the dynamic Brazilian striker from the card, and that Silva is expected to be back in play by December.

Silva, a native of Sao Paulo, Brazil, who burst onto the scene in the Fury FC promotion, has racked up four back-to-back victories in the Octagon against James Irvin (Pictures), Tomasz Drwal (Pictures), Houston Alexander (Pictures), and Antonio Mendes (Pictures). The lanky 25-year-old stopped three of those four opponents with TKOs in the first round, with Polish standout Drwal the only one to hang on into the second stanza.

In May, Brazilian jiu-jitsu black belt Silva (13-0) submitted Mendes with punches at UFC 84 “Ill Will” in Las Vegas.

A replacement for the undefeated Machida (13-0), who shut out former UFC champion Tito Ortiz (Pictures) with a three-round unanimous decision at UFC 84, has not been named at this time.