Former WBO heavyweight boxing champion Ray Mercer will have a little more of Tim Sylvia to contend with when the pair meet Saturday night at Adrenaline III inside the BJCC Arena in Birmingham, Ala., for an impromptu MMA bout.

The 6-foot-8 Maine native usually sheds down to within five pounds of the 265-pound heavyweight limit during competition. However, Sylvia weighed in Friday at 311 pounds to Mercer’s 257-pound frame –- a far cry from the former UFC champion’s usual tale of the tape.

The bout, originally intended as a six-round boxing match, has fended off criticism since its inception. It took its biggest hit yet Thursday when athletic commission reps stepped in to squash it all together, claiming it had not been properly approved and regulated.

At the insistence of both Mercer and Sylvia, Adrenaline promoter Monte Cox has since changed the headliner to an MMA tilt; Cox said he could not secure new regulation for the event in time.

This new arrangement puts Mercer –- who had one previous MMA fight against Kevin “Kimbo Slice” Ferguson in 2007 -- at a certain disadvantage should it hit the canvas.

Whether Sylvia and Mercer will keep the bout within their preferred realms of expertise will be up to them.

Other Adrenaline III weights:

Tuan Pfam (126) vs. Sean Hall (123.6)
Nick Rossborough (184.6) vs. Keith Johnson (182.6)
Josh Barnes (270) vs. Brad Tidwell (330)
Juan Zapata (160) vs. Joe Jordan (170.8)
Bryan Goldsby (135.6) vs. Joey Marimberga (136)
John Salter (184.6) vs. Roberto Traven (183)
Sasuke Zapata (165.6) vs. Rich Clementi (170.2)
Chris Davis (203.2) vs. Jeremy Horn (204.8)

Amateur Bouts
Daniel Ritchie (171) vs. Adrian Miles (171)
Barry Clifford (166.4) vs. Matt Smart (170.8)
Keith Cunagin (182) vs. Cory Hamrick (180.4)
Justin Traweek (335) vs. Brandon Esch (302)
Ron Mitchell (226.8) vs. Brandon Powell (236.8)