Still bothered by a jammed right toe, star guard Ty Lawson is a likely no-go when top-seeded North Carolina opens in the NCAA men's basketball tournament today.

Does it matter?

 The Tar Heels — President Obama's pick to win it all — remain prohibitive favorites to roll past Radford in the tournament's South Region and add the Highlanders to a long, uninterrupted list of beaten-down No. 16 seeds. Top seeds are 96-0 in first-round games, winning last year by an average of 31 points.

 A second No. 1 seed, Connecticut in the West, also plays today vs. Chattanooga as 16 first-round games tip off in three of the four regions — all but the Midwest.

 Lawson, the Atlantic Coast Conference Player of the Year as a junior, sat out Carolina's two ACC tournament games with the toe injury, and coach Roy Williams dampened hopes Wednesday that he'd return as soon as the Radford game. "There is a huge, huge probability that Ty will not play," Williams said.

 Said the Tar Heels' Wayne Ellington, "We've been preparing without him so far. It's tough to lose such a major piece, but at the same time it's a challenge for us. Guys have to elevate their game and step up."

 Elsewhere today:

 Blake Griffin, the likely national Player of the Year, and No. 2-seeded Oklahoma open in the south against Mid-Eastern Athletic Conference champion Morgan State.

 Memphis, seeded second behind UConn in the West, meets Cal State Northridge — the Tigers' first tournament game since surrendering a nine-point lead in the final 2 1/2 minutes of regulation and losing to Kansas in overtime in last year's tournament final in San Antonio.