The first meeting of the expected top two men's teams in the conference was close for about 21 minutes.
After its second possession of the second half Niagara had a 43-42 lead.
And, then, it was never close again. Siena ran off the next nine points and the visitors never got closer than six points after that.
The Saints dominated the final 19 minutes on their way to an 83-65 victory over the Purple Eagles in a Saturday afternoon contest before a crowd of 8,065 at the Times Union Center in Albany, N.Y.
Siena is now 5-0 in conference play (12-4 overall) and remains the only unbeaten team in league contests. Niagara fell to 3-2 and 10-7.
Siena has won the last two conference titles and all the evidence so far indicates that string will reach three. In the Saints' five conference contests they have outscored opponents by an average of 18 points.
Saturday's setback was the most-lopsided suffered by Niagara to date, its previous largest losing margin had been 12 against Akron.
"They were the best team today, no doubt about it," said Niagara coach Joe Mihalich, about Siena. "They've got a lot of ways to beat you. If it's not one thing, it's the other. There's no margin for error against these guys."
Mihalich's team, though, made plenty of errors, particularly in the second half when its defense suddenly faltered and its offense got shut down by a stiffling Siena defense.
"They (Siena) didn't do anything different in the second half," said Niagara's Tyrone Lewis. "It was us. We weren't tough enough. When you play a team like Siena that's a real good team you have to be almost perfect and we weren't."
Siena forward Edwin Ubiles also continued to make his case for Player of the Year honors. The 6-foot-6 senior finished with a game-high 25 points on 11-of-19 shooting. He scored 19 of those points in the game's final 21:30.
Niagara's counterpart to Ubiles, the 6-5 senior forward Bilal Benn, couldn't match the Siena standout scoring just seven points on 3-of-12 shooting and getting seven rebounds.
"I can't tell you what happened to him," said Mihalich, about Benn. "He seemed ready to go before the game. He just didn't have one of his better nights."
Saints' coach Fran McCaffery heaped praise on his team's inclination to do the necessary dirty work Saturday.
"The key to the game was how we played defense in the second half," said McCaffery. "We defended better and we rebounded better. Any time you play a team as talented as Niagara you have to defend and rebound or it's going to be a long night."
Siena outrebounded the visitors, 43-36 (junior center Ryan Rossiter had 12 rebounds, while freshman forward O.D. Anosike had his best game to date with nine rebounds), and Siena held the Purple Eagles to 35.8 percent shooting in the game, including 23.5 percent in the second half.