COVID-19 has knocked out this weekend's UFC main event.

The Curtis Blaydes vs. Derrick Lewis heavyweight contender bout scheduled for UFC Fight Night in Las Vegas on Saturday is off after Blaydes tested positive for coronavirus, sources told ESPN's Ariel Helwani.

The UFC is hoping to reschedule Blaydes vs. Lewis for UFC 256 on Dec. 12, sources told ESPN, but no deal is done yet.

ESPN has Blaydes ranked No. 3 and Lewis ranked No. 5 in the world at heavyweight.

The scheduled UFC Fight Night co-main event -- a light heavyweight bout between Anthony Smith and Devin Clark -- will move up to feature fight status, sources told ESPN's Brett Okamoto (prelims on ESPN+ at 8 p.m. ET; main card starts on ESPN2/ESPN+ at 10 p.m. ET).