Frantz Massenat led Drexel with 17 points, and redshirt freshman Tavon Allen added 16 in his first collegiate start after scoring 15 off the bench in a 61-59 win over Penn last weekend.
Yet Dellavedova - who started for the Australian squad that reached the Olympic quarterfinals in London - made the biggest impression on Dragons coach Bruiser Flint.
"He's a tough kid to play against," Flint said. "One of the things you've got to worry about with him is that he's a good passer. You can't be throwing three guys at him, because he's going to find the guy who's open.
"He got guys the ball when they needed it. When they needed buckets, he got them. He really makes the other kids on the team a lot better."
The Dragons began the second half by making four successive baskets to draw within 40-38 with 17 minutes, 22 seconds to play. Then Dellavedova and Brad Waldow scored five points each in a 10-3 surge that gave the Gaels a 50-41 lead with 14:33 left.
Drexel's offense collapsed late. The Dragons made only one basket in a span of 6:11, while scoring seven points on free throws, and St. Mary's led by as many as 15.
"I thought we played hard, but I didn't think we played smart," Flint said. "A big part of the game, I didn't think we played tough enough. We didn't do our job in the heat of the game, being in certain places, doing certain things."
Bruiser Flint said after the game that no decision has been reached on whether senior Chris Fouch will request a medical redshirt year from the NCAA. Fouch, Drexel's leading scorer (16.7 points per game), has undergone surgery for a fractured right ankle suffered against Penn last Saturday. "The surgery went well," Flint said. "Now, it's all about rehab for him" . . . Flint said sophomore Damion Lee is expected to play Friday. Lee has missed the last two games after taking a hard fall in Drexel's overtime loss to Illinois State last Thursday.