Barker, Phillips, Woodyard, Leonard and Reeves all come inPaul Sturrock made five changes to the side that lost 2-1 to Northampton on Saturday for the visit of Leyton Orient in the Johnstone's Paint Trophy.
The good news for Blues was that Chris Barker and Mark Phillips both passed late fitness tests to be available for the game.
With Michael Spillane cup-tied, Alex Woodyard came in to the middle of midfield, while Danny Mayor made way for first-leg match winner Ryan Leonard.
The final change saw Ben Reeves, rested at the weekend, return to the starting XI in place of Barry Corr.
Corr, Freddy Eastwood, Anthony Straker, Daniel Bentley and Mayor were on the substitutes bench.
Blues: Smith; Clohessy, Phillips, Prosser, Barker; Hurst, Leonard, Woodyard, Lund; Reeves, Assombalonga.
Subs: Eastwood, Straker, Bentley, Mayor, Corr.