Cave, who was part of the Ireland Under-20s' Grand Slam-winning team this year, has been in electric form of late at club level, scoring two hat-tricks over successive weekends for Belfast Harlequins. Saturday's game will mark his first competitive start for Ulster.
Bartholomeusz is preferred to Bryn Cunningham at full-back, while number 9 Marshall is looking forward to making his first start for Ulster, with Kieran Campbell dropping to the replacements bench.
"This is my first start for Ulster, I feel confident and I'm looking forward to getting some more game-time," said Marshall.
"David Humphreys has been giving me some good advice this week which has been really helpful. We have done all our preparation and we know what we need to do on Saturday."
The two changes in the forwards see Declan Fitzpatrick taking over from Tom Court at tighthead prop and following Ryan Caldwell's three-week suspension for stamping, Justin Harrison will partner Tim Barker in the second row for the Rodney Parade tie.
Ulster have also shaken up their bench with Italian World Cup lock Carlo Del Fava in line to make his competitive debut for the province as a replacement and summer signing Kieran Hallett, the back-up out-half, could do likewise.
ULSTER: Mark Bartholomeusz; Mark McCrea, Darren Cave, Tommy Bowe, Simon Danielli; Niall O'Connor, Paul Marshall; Justin Fitzpatrick, Nigel Brady, Declan Fitzpatrick, Justin Harrison, Tim Barker, Matt McCullough, David Pollock, Roger Wilson (capt).
Replacements: Matt Miles, Tom Court, Carlo Del Fava, Neil McMillan, Kieran Campbell, Kieran Hallett, Bryn Cunningham.