The fans stormed the court at Hagan Arena, an impromptu celebration that caught the St. Joseph's players by surprise.

Then again, beating a previously undefeated and nationally ranked team will cause this type of reaction.

In what was their most impressive win of a season that has already shown great improvement, St. Joseph's defeated Creighton, 80-71, on Saturday afternoon before an appreciative crowd that let out its emotions after the final buzzer.

"It's definitely felt great to see the fans so excited and it's the first time it has happened to me since I've been here," said junior guard Carl Jones.

Actually, Jones is one of the main reasons the fans were celebrating. He scored 20 of his game-high 29 points in the second half.

In winning, the Hawks improved to 7-3 and are now 4-0 at Hagan Arena, with Villanova visiting there on Saturday. Creighton (7-1) is ranked No. 17 in the USA Today/ESPN Coaches Poll and No. 19 by The Associated Press.

The Hawks also received a huge effort from 6-foot-8 sophomore Ronald Roberts, a sixth man who offers starter's minutes and production.

Roberts had 12 points, six rebounds, three blocked shots and one of the most spectacular dunks, a tomahawk jam on a feed from Jones.

"What was he, 11 feet in the air when the threw it down?" asked an amazed St. Joseph's coach Phil Martelli.

The Hawks trailed by as many as eight points in the first half, but led 35-30 by intermission. Roberts had seven points and six rebounds in the first half and held the fort when center C.J. Aiken and forward Halil Kanacevic both sat extend minutes after each drew two first-half fouls.

"We had guys in foul trouble and I had to step up, play hard and play smart," Roberts said.

Creighton was led by 6-7 sophomore all-American candidate Doug McDermott, who had 26 points and was the main reason so many NBA scouts were in attendance. He hit 5 of 7 shots from beyond the arc, but was limited to just 16 field goal attempts.

The key was that St. Joseph's beat Creighton at its own game. The Bluejays entered the contest averaging 87 points per game. St. Joseph's continually switched defenses, alternating between man-to-man and zone and Creighton wasn't able to run-and-gun so much.

"They often showed zone but they were really playing man-to-man and we got a little rattled," said McDermott, the son of coach Greg McDermott.

When C.J. Aiken scored an alley-oop dunk to extend the Hawks lead to 67-55 with 1:49 left, it looked over, but Creighton would cut it to 69-63 with 1:01 left.

Jones then made a driving layup and ensuing free throw and the fans could begin making their celebration plans.

Contact staff writer Marc Narducci at 856-779-3225, mnarducci@phillynews.com, or @sjnard on Twitter