Bringing a bit more bulk into a relatively light Waratahs pack, Latu will lock horns with the Lions' in-form rake Marx, who has been a scrummaging, ball-poaching menace in the South Africans' run to the playoffs.
"I think he's going to bring a lot of power in the middle of that scrum there," Wallabies prop Kepu said of Latu.
"They've got Malcolm Marx from the Lions, he's a great scrummager and he's been playing really good rugby.
"Someone like Tolu can match him in that area and around the park he's been great for us coming on in the second half of our games."
With incumbent hooker Tatafu Polota-Nau unavailable and Jordan Uelese injured, Latu was drafted into the Wallabies squad for the Ireland series, and coach Michael Cheika's faith helped rejuvenate his Super Rugby form.
"In the June period or leading up to that with the Wallabies he really sort of took his opportunities," Kepu said.
"In the last few weeks he's shown himself putting his mind to the work that's needed, all the extras and everything that guys do off the field and away from the training paddock.
"That's what he's worked on really hard and he's starting to show it on the field."
The Waratahs, champions in 2014, lost their only other playoff in South Africa to the Cape Town-based Stormers in 2010.
They face a huge task to fell the Lions, who are looking to claim their maiden championship after losing in the title-decider the last two years.
"It's going to be a mountain of a challenge but it doesn't get any better playing in Johannesburg against a great Lions team," said Kepu.
The Canterbury Crusaders host fellow New Zealanders Wellington Hurricanes in the other semi-final in Christchurch on Saturday.
(Editing by Peter Rutherford)
