The third qualifying round encounter at Dales Lane (kick-off 3.00pm) will see the winner progressing to Monday's fourth and final qualifying round – and being £5,625 better off.
United boss Ian Culverhouse will check on his walking wounded – with a clutch of players having missed last weekend's 1-0 win over Chester FC.
Rushall made a slow start to life in National League North, but have since won three of their last four encounters, with wins over Peterborough Sports, Bishop's Stortford and Scarborough Athletic.
While United were beating Leamington 4-0 in the previous round, Rushall were edging past Carlton Town (3-2).
Should Saturday's tie end all-square, the replay will be played at the Jakemans Community Stadium on Tuesday evening (kick-off 7.45pm).
LIVE COVERAGE
BBC Radio Lincolnshire full-match commentary, courtesy of Dale Storey and Craig Singleton, is available.
Twitter updates will be available via @bostonunited throughout the afternoon.
TICKETS
Away supporters can purchase tickets here.
KIT WATCH
United will be wearing their third kit of all-white.
PIC: Oliver Atkin.