Amy Kaplan of FanSided MMA first reported the news.
Lopez (11-5-0) is winless thus far in the UFC, having dropped a bout to Merab Dvalishvili at UFC Fight Night: Eye vs. Calvillo. Lopez is a former Combate Americas bantamweight champion and he relinquished the title upon signing with the UFC. Lopez has competed 16 times as a professional MMA fighter and just four of those bouts went the distance.
Birchak (16-6-0) will start his second run with the UFC and the fighter earned a record of 2-2-0 during that first run. Birchak returns to the UFC on a three-fight winning streak, which includes two wins in the Combate Americas promotion. Birchak is also competing for the first time in over a year, as his last bout happened in October of last year.
UFC Vegas 13 takes place on Saturday, November 7 from the UFC Apex in Las Vegas, Nevada with Thiago Santos and Glover Teixeira headlining. Fightful is providing live coverage of the event, which airs live on ESPN 2.