Undefeated featherweight prospect Erik Koch is the latest fighter to withdraw from the WEC 43 event as a undisclosed injury has forced him out of his undercard bout against former IFL featherweight champ Wagnney Fabiano.

Replacing Koch will be WEC newcomer and Miguel Torres-managed fighter, Mackens Semerzier. News of Koch's injury and Semerzier's insertion in the bout was first reported by Matt Erickson at NWI.com.

Semerzier was originally booked to fight Josh Rave at a CageFest event on Oct. 3, however, the fighter jumped at the opportunity when the WEC came calling. The WEC is considered the premier promotion for fighters who fight in the featherweight and bantamweight divisions.

Semezier most recently defeated Kenny Foster at a Elite Fighting Challenge event in June. The former Marine is off to a 4-0 start to his professional MMA career, with all of his wins coming by stoppage. For those who have not seen Semezier in action, he has shown to have heavy hands and a highly regarded ground game as he holds a purple belt in Gracie jiu-jitsu.

Fabiano has won his last eight bouts, which include his first two bouts in the WEC against Akitoshi Tamura and most recently Fredson Paixao. Prior to entering the WEC, Fabiano went 5-0 in the now-defunct IFL organization, with wins over the likes of John Gunderson, Shad Lierley and L.C. Davis.

The Nova Uniao fighter, Fabiano, hasn't tasted defeat since suffering his lone career loss against WEC veteran Jeff Curran in October 2006. He sports a 12-1 overall MMA record, with nine of his wins coming via stoppage, including seven by submission. Fabiano holds other notable wins in his career over Tommy Lee, Matt Fiordirosa and Bao Quach.

WEC 43 will take place on Oct. 10 at the AT&T Center in San Antonio, TX, and the main card will air live on Versus. The event's headliner is a WEC interim lightweight title bout between Donald Cerrone and Benson Henderson.

Also in action, former WEC lightweight title contender Rich Crunkilton returns after more than 18-months off, due to injuries, to take on undefeated prospect Dave Jansen.