Powerful prop Macklin broke his ankle in September during his last outing with the Ravens, while the Ireland-capped Cave has been out since November with a hamstring injury.
The Ravens squad is made up of a mixture of contracted players, Academy members and promising club players.
The selected team includes lock Neil McComb and Connacht-bound duo Mark McCrea and Niall O'Connor. Tommy Seymour, Jamie Smith and Conor Gaston make up an exciting back-three.
Moseley are currently second from bottom in the English Championship, but Ravens boss Gary Longwell will not be taking the opposition lightly.
"It's a good opportunity for the young players to come up against quality opposition like Moseley," he said.
"This season we've been represented by a mixture of Academy players and young members of the senior squad and it's been a steep learning curve."
The Ravens have won one of their four cup games this season, and lie fifth in the Pool C table ahead of the final round of matches.
Tickets for Wednesday's clash with Moseley are priced at £15 (adult Stand), £12 (adult Promenade/Terrace) and £8 (children). Ulster Rugby Season Ticket holders can gain entry as part of their package.
ULSTER RAVENS (v Moseley): Jamie Smith; Tommy Seymour, Darren Cave, Mark McCrea, Conor Gaston; Niall O'Connor, Michael Heaney; Conor Carey, John Burns, Adam Macklin, David Huston, Neil McComb, David Bradford, David McGuigan, Robbie Diack (capt).
Replacements: Jonny Murphy, Kyle McCall, Alan Whitten, Paul Pritchard, Conor Spence, Michael Allen, David McIlwaine.