The No. 12/18 Hornets (25-8) scored two runs in the second to take a lead they would not relinquish against the Cougars (24-17).
The winner of Saturday's game will have two chances to win the USA South Conference baseball championship.
With a 6-2 lead thanks to two runs in the top of the eighth, SU saw Averett make things interesting by scoring three runs in the bottom half of the frame.
The save was Scallion's third of the spring and he retired AU in order in the ninth.
The Hornets final two runs, which came courtesy of a Tucker Brown two-run dinger, were unearned. Cory Nelson led off the SU eighth by reaching on an error and after being sacrificed to second and seeing Michael Paul strike out swinging, Brown took Cougars reliever Chris Moyer deep for Shenandoah's fourth home run of the tourney.
Vince Claudio (5-1) earned the win after allowing five runs (four earned) on four hits and four walks in 7.0 innings.