David's excellent efficiency preview available here and at HackTheBracket (along with 31 other previews of equal quality). Niagara is better than a typical 16-seed and their offensive efficiency is their clear strength. Unfortunately for the Purple Eagles, their offensive efficiency is a clear strength in part due to their defensive efficiency being a clear weakness.
Considering that Niagara's three toughest games consisted of (with efficiency margins in the parentheses) hosting Akron (-25), hosting St. John's (-33), and playing Holy Cross (+13) at neutral site, their performance in at-risk games (admittedly impacted by leading scorer Charron Fisher missing 7 of Niagara's 25 at-risk games, including the losses to Akron and St. John's) doesn't suggest they can expect to compete with Kansas for 40 minutes.
NIAGARA OFFENSE v. KANSAS DEFENSE
(at-risk games only)
Niagara will likely shoot even worse than normal from the field against Kansas's defense and it's even more unlikely that Niagara will be able to match their usual offensive rebounding rate. Even with his outstanding shooting performance Tuesday night in Dayton, Clif Brown is just a 46.4 eFG% shooter on the season. Charron Fisher (50.9 eFG%), Tyrone Lewis (50.2 eFG%), and JR Duffey (51.4 eFG%) all shoot better than Brown, but none of them would rank higher than 7th in eFG% on Kansas's stat sheet. If they're struggling to create easy shots against the 288th rated defensive schedule in the country, then Kansas should cause them fits.
Let me make this clear: Kansas is an oustanding defensive team. There are other important factors for the team entering the NCAA Tournament: pace of play (Niagara should cooperate with that in the first round), field goal shooting (just 49.1 eFG% in the Big 12 Tournament), and health (I'd rather they not have to try and win six games in a row without one or more members of the eight-man rotation) but any prolonged success they have in this tournament will be due first and foremost to their defense.
In Ken Pomeroy's adjusted defensive efficiency rankings, Kansas is 2.8 points per 100 possessions better than the second-placed team. The difference between first and second is greater than the difference between the second- and twelfth-ranked teams.
Kansas emerged as a national title contender because their offense improved over the course of the season but the underlying, constant reason for Kansas's recent success has been the team's defensive play. (Again, David represents this excellently in graph form.)
NIAGARA DEFENSE v. KANSAS OFFENSE
(at-risk games only)
That Kansas's offensive improvement coincided with them playing mostly mediocre-to-poor Big 12 teams shouldn't hide the very real improvements they've made offensively over the course of the season.
This team couldn't get more than a point per possession against Oral Roberts, Ball State, DePaul, USC, or Toledo in their first ten games. What felt like an offensive explosion against Boston College right before Christmas (1.12 points per possession) was bettered ten times in Big 12 play including the Big 12 Tournament Championship game against Texas, wherein the Jayhawks created far more good shots than they converted.
While I agree that Niagara got a raw deal in having to win the play-in game to make the bracket proper (and probably got a raw deal in being seeding 16th to begin with--the committee clearly did not take Charron Fisher's 8-game absence into account), I can't foresee them giving Kansas too much trouble tomorrow night. Kansas is not just good at more things than Niagara, they're better than they Niagara is the things Niagara are good at.
Prediction: Kansas 84 Niagara 64