As seen on RAW last night, Braun Strowman left Brock Lesnar laying after being challenged to the ring by Lesnar and Paul Heyman. Heyman made it a point during his promo to state that Lesnar is the underdog heading into his match with Strowman at No Mercy on September 25th.
Dave Meltzer noted on the latest edition of Wrestling Observer Radio that the original plan was for Lesnar to retain the title at No Mercy.
Lesnar's appearance on RAW last night was his last date before the pay-per-view, as Lesnar isn't scheduled for next week's RAW at the SAP Center in San Jose, California, which is the go-home show for No Mercy. Meltzer noted that it was WWE's call to not use one of Lesnar's dates for the go-home show and instead use it for last night's RAW. Strowman is scheduled for next week's RAW.
Lesnar did film some material last night that will air on next week's RAW, so he will have a presence on the show despite not being there. As of this writing, Lesnar is not advertised for any upcoming RAW shows, including the post-No Mercy RAW on September 25th in Ontario, California.