Kim O'Reilly, CBS Sports

There is a new team on the top line of the projected bracket for the first time since the NCAA Tournament selection committee revealed Purdue, UConn, Houston and Arizona as its four No. 1 seeds last Saturday.  

The Wildcats have dropped to a No. 2 seed In Friday's updated Bracketology, after losing at home to Washington State on Thursday. North Carolina is now the fourth No. 1 seed and will be placed in the West Regional.  

Arizona and UNC's resumes are pretty similar. North Carolina has slightly better wins – 11 in Quad 1 and Quad 2 vs. 10 for Arizona in the top two quadrants. Their losses are even closer together, but are slightly in the Tar Heels' favor.  

The Wildcats have been hampered by the quality of their league. Five of their seven Quad 3 wins are Pac-12 games. Not that the ACC has been stellar, especially by its standards, but most of their also-ran teams live in Quad 2.

So, obviously, the battle for the fourth spot is not over yet, but the gap between the top three and No. 4 just got bigger. Purdue, UConn and Houston are each at least two losses away from even being considered for the fourth No. 1 spot, let alone dropping off the top line entirely. It is an even bigger gap for Purdue because the Boilermakers have neutral court wins over three of the four current No. 2 seeds.

Bracketology top seeds

Check out Palm's latest bracket, Bubble Watch and full field of 68 at the Bracketology hub.