In 2008-2009, the Villanova Wildcats had a great NCAA tournament run while playing man defense pretty much 100% of the time. Against UCLA and Duke that year, Jay Wright's man defense produced the kind of score lines that we usually only see during the early-season schedule.
In 2009-2010, while the defense struggled in the trapping and switching system, Jay Wright introduced some limited zone defense. This was mostly in the form of a triangle-and-two set (discussed here, and here), which puts two players on man-coverage of opposing team stars, while the other three play a triangular zone in the half-court.
The triangle-and-two is a junk defense, but the 2-3 zone run by Jim Boeheim at Syracuse is a very real defensive option. Other teams also run a 3-2 zone (shifting an extra man to the perimeter), or a 1-3-1. While Syracuse runs their 2-3 zone the vast majority of the time, a lot of great coaches switch off between different defenses.
In fact, during the early portion of Jay Wright's tenure, his teams did play (and he did coach) mostly zone defense -- a match-up zone and 3-quarter-court zone in particular -- during the suspension-afflicted 2003-2004 season. Wright ran the zone that season mostly out of necessity, however, and while he has expressed an interest in keeping the zone "in his back pocket," he has also expressed a belief that it can be a detriment if not used full-time:
I just feel like with the three point shot, unless you make it you're bread-and-butter defense is always susceptible to giving up threes and offensive rebounds. That's the two areas we try to be successful - in our rebound margin and in the three point defensive percentage.
Even when the zone is your primary defense, rebounding will suffer. For example, Syracuse's defense was ranked 260th in rebounding last season by Ken Pomeroy. As for three-point defense, Syracuse's 2-3 zone was rated only slightly worse against the 3 (22nd) than it was rated overall (18th).
So who is right? Coach Wright believes that his defense is best-off by executing it's man-to-man defense well and keeping that zone buried deep in his back pocket. Wright's man defense takes time to solidify, requiring players to master it's trapping and switching as well as knowing when to take calculated risks.
Still, if the defense struggles this season, some will call for Jay Wright to switch off to a zone defense. Should the Wildcats keep the zone buried deep in that back pocket, or should Coach Wright pull it out more often?