The PSL rivals will ignite hostilities at 18h00 (SA time) at the Independence Stadium, with the victor meeting either Tigers FC or African Stars in Sunday's final.
Sundowns are bidding for a hat-trick of triumphs at the pre-season competition.
“Since I have been with Sundowns one thing has been clear, there are no friendly matches," Mohomi told the club's website.
“The intensity is always high, and now that this is a high-profile friendly one can expect a highly contested match," added the former Free State Stars midfielder, who forms part of a strong 30-man squad in Windhoek.
Downs coach Pitso Mosimane is minus injured trio Asavela Mbekile (shoulder), Kennedy Mweene (groin) and Mzikayise Mashaba (hernia), but will unleash marquee signing Sibusiso Vilakazi against the Buccaneers.