Audavion Collins and Dejuan Lane notched their first career interceptions against the Terrapins.
Wallace is Penn State's second-leading receiver with 35 receptions, 279 yards, and three touchdowns.
Nolan Rucci, JB Nelson, Cooper Cousins, Eagan Boyer, and J'ven Williams are among those who could see more playing time.
Penn State was seeded No. 6 and is projected to face No. 11-seeded Indiana.
Singleton and Allen have combined for 100 yards twice in the last six games.
Elliot Washington II and Kaden Saunders are listed as out.