Saddler hit consecutive 3-pointers to give the fifth-seeded Blue Hens (18-12) a 59-55 lead with 6:06 remaining. The 12th-seeded Tigers (1-31) had tied it after trailing by as many as 18 points in the first half and 36-25 at halftime.
Robert Nwankwo led Towson with 27 points and 20 rebounds, both career highs for the senior forward. His 19 points and 12 rebounds in the second half led the Tigers' rally.
The victory was Delaware's ninth in a row, its most since it won 13 straight in the 1998-99 season. Jarvis Threatt added 15 points and Josh Brinkley 14 for the Blue Hens, who will play No. 4 seed Old Dominion on Saturday in the quarterfinals.
Towson lost its ninth straight.