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I've been compiling Selection Sunday bracket projections for SI.com for eight years, and this one was by far the hardest due to mass uncertainty at both the top and the bottom of the bracket.

Normally going into the last day you can be reasonably certain about at least three of the four No. 1 seeds. This year, the only 100 percent certainty is Ohio State (which is my No. 1 overall seed). On paper, UCLA clearly deserves a top seed as well but the committee might punish the Bruins for their consecutive bad losses to end the season. Beyond that, it's anyone's best guess which two or three teams the committee will tab from among Wisconsin, Florida, North Carolina, Kansas and Georgetown. I went with the Badgers and Tar Heels due to their strong overall resumes. Four of the five aforementioned teams play title games on Sunday that could be the deciding factor.

Meanwhile, NC State and Arkansas have the chance to lock up automatic berths on Sunday that would bounce the last two current at-large teams. The last four teams on this bracket are, in order, Stanford, Texas Tech, Drexel and Illinois. The last four teams out were Kansas State, Purdue, Arkansas and Air Force.

For a more detailed bubble breakdown, click here.

The chart below is designed like an actual bracket sheet, with the regions on the left-hand side (East and West) meeting in one semifinal and the regions on the right-hand side (Midwest and South) meeting in the other. Note that the pairings are based on the order of the No. 1 seeds.

* -- Faces Northwestern State in Southland championship game on Sunday.