Gabriel "will serve as the backup quarterback" Sunday against the Saints, Jeremy Fowler of ESPN.com reports.
It was announced earlier in the week that Shedeur Sanders would start Sunday's contest with Deshaun Watson in concussion protocol, and although Watson has not officially been ruled out for Week 9 as of yet, he reportedly will be. That will leave the backup spot to Gabriel, but presumably for only one contest, as the report notes Watson is expected back for Week 10.