Back in May, ESPN’s Jay Williams reported that Duke junior center Mason Plumlee was going to test the NBA waters. It appeared to be a brutal blow to the Blue Devils, who were already losing his brother Miles to graduation, and leading scorer Austin Rivers, who departed after his freshman year. On the heels of a first round NCAA exit to 15th seeded Lehigh, the 2012-2013 outlook for Duke appeared bleak.

In early April, Plumlee made the decision to return to Durham. Based on the first month of the season, it’s not an exaggeration to say that his staying at Duke was the biggest offseason decision – Cody Zeller never appeared to consider the NBA – in college basketball.

Plumlee scored 21 points and took 17 rebounds Wednesday, sparking a 2nd half rally to lead Duke over Ohio State, 73-67. Duke is unbeaten at 7-0, and in its three biggest games of the young season, Plumlee has been instrumental in victory:

Plumlee vs. Kentucky: 18 points, 7-of-8 FGs
Plumlee vs. Louisville: 16 points, seven rebounds
Plumlee vs. Ohio State: five offensive rebounds, 9-of-12 FTs

Obviously Seth Curry has improved (15.1 ppg), and freshman Rasheed Sulaimon has been a spark (41 percent 3-pointers), but Plumlee has been the man inside.

The biggest difference in Plumlee’s game – besides being significantly more assertive around the basket – is his free throw shooting (78.9 percent). Last year? He shot 52.8 percent from the line. He’s no longer a liability at the line. Plumlee’s draft stock is soaring – right now, he looks like a Top 5 pick (in a weak draft; we’ll have another mock draft tomorrow) – and I have already circled Jan. 26 on my calendar: Plumlee vs. Maryland’s Alex Len in a battle between two of the best big men in college basketball.