Koch looked impressive in a win over Shane Campbell at UFC Fight Night 88, but has fought only three times over the last two and a half years.
Koch’s replacement, 26-year-old California native Jason Gonzalez (10-2-0), will make his octagon doubt.
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Gonzalez is currently on a six-fight win streak, including a TKO over Chris Padillia at RFA 38.
UFC here I come! Making my UFC debut Sept 10th on the overeem card! Let's get this!!! pic.twitter.com/b6GXpijhTR
— Jason Gonzalez (@JasonGonzalez55) August 12, 2016
The 27-year-old Dober defeated Scott Holtzman by unanimous decision at UFC 195.
UFC 203 takes place September 10th at the Quicken Loans Arena in Cleveland. Heavyweight champion Stipe Miocic defends against Alistair Overeem in the main event.