The UFC made the announcement of the injury on Friday morning. Maia will not get a replacement opponent, and the card will proceed with 12 scheduled fights.
Koscheck (17-7), the No. 10 welterweight in the UFC, is currently on a two-fight losing streak after dropping a split decision to Johny Hendricks and falling to TKO to Robbie Lawler.
Maia (18-4) is 3-0 since dropping to welterweight, defeating Dong Hyun Kim, Rick Story and Jon Fitch. That run has earned Maia the No. 5 ranking in the welterweight division.
No specifics were given on Koscheck’s injury or if the fight would be rescheduled for a later card.
UFC 163 will take place Aug. 3 from the HSBC Arena in Rio De Janeiro, Brazil. The event will be headlined by a featherweight title bout, as champion Jose Aldo will put his title on the line against Chan Sung Jung.
Jung is an injury replacement for Aldo’s original opponent, former WEC lightweight champion Anthony Pettis.
Full UFC 163 Fight Card
Jose Aldo vs. Chan Sung Jung (for featherweight title)
Phil Davis vs. Lyoto Machida
Cezar Ferreira vs. Clint Hester
John Lineker vs. Phil Harris
Vinny Magalhaes vs. Anthony Perosh
Sheila Gaff vs. Amanda Nunes
Neil Magny vs. Sergio Moraes
Thales Leites vs. Tom Watson
Josh Clopton vs. Rani Yahya
Ian McCall vs. Iliarde Santos
Viscardi Andrade vs. Bristol Marunde
Robert Drysdale vs. Ednaldo Oliveira