Wales and Cardiff flanker Navidi and Wales and Ospreys lock Beard were late Lions call-ups for the tour of South Africa after injury struck their fellow countrymen Justin Tipuric and Alun Wyn Jones.
The pair haven’t played in the Lions’ two wins so far – the warm-up success over Japan in Edinburgh and the opening tour win over South African province Lions.
Navidi and Beard are joined in the starting line-up against the Sharks by full-back Liam Williams and half-backs Gareth Davies and Dan Biggar.
Wednesday’s game will be Davies’ first Lions start after he came off the bench for his debut against the Lions.
Wales hooker Ken Owens is on the bench with the starting side captained by Ireland and Ulster lock Iain Henderson.
“It’s a quick turnaround from Saturday, but we’ll be ready to go by Wednesday night,” said Lions head coach Warren Gatland.
“I’m pleased we managed to come through the weekend’s game unscathed and the boys have rested and recovered well.
“We feel like we’re slowly building but, as ever, there is still room for improvement in all facets of our game.
“Wednesday night is another chance for us to have a look at a few more combinations. I’m looking forward to seeing how the back-row goes.
“It’s an exciting mixture and one we hope will offer something a bit different.”
Navidi is joined in the Lions back-row against the Sharks by England pair Tom Curry and Sam Simmonds. Curry will also make his Lions debut.
Beard and Henderson form the second-row pairing with a front row of Mako Vunipola, Luke Cowan-Dickie and Zander Fagerson.
Williams is joined in the back three Anthony Watson and Duhan van der Merwe with Bundee Aki and Elliot Daly the centre pairing.
Scarlets and Wales hooker Owens is joined on the bench by Rory Sutherland, Tadhg Furlong, Tadhg Beirne, Jack Conan, Conor Murray, Stuart Hogg and Chris Harris.
“We expect another physical test against a side who are known for their power play and ambition,” said Gatland.
“My congratulations to Tom, Josh and Adam ahead of their first starts in a Lions jersey.”
