Let's take at look at how Brice Johnson compares to Sean May, Tyler Hansbrough and Tyler Zeller.
One rather large caveat is the sample size, Johnson has played 1/3 of the schedule(counting probable postseason games.) That means there could and probably will be some moderation to his numbers. In particular Johnson's offensive rating is astronomical and 20.5 points higher than it was last season. Only one player in the Roy Williams era has finished above 130 in offensive rating and that was Ty Lawson's 134.3 in 2009 which was the best in the country.
It stands to reason that Johnson's rating is going to settle, the question is how much? It should be noted that Johnson's offensive rating in ACC play last season was 119.4, fifth in the ACC. In short, Johnson is on pace to produce a very high offensive rating, possibly something along the lines of what Tyler Hansbrough posted in 2008 when he was ACC and national player of the year.
A couple of notable differences between Johnson and the other three. One is the usage aka the possession rate. Johnson has the ball far less than his predecessors. On one hand, when Kennedy Meeks returns Johnson should not see a drop in his usage given it is already on the lower side. On the other hand, as efficient as Johnson has been and an eFG% that is in the mid-60s(!) the argument can be made he should be getting more touches than he does right now.
Another area Johnson could improve on is his free throw rate. At present Johnson has an FTR of 36.4. The other three Tar Heel big men were above 50 with Hansbrough's 70.5 leading the way. Since Johnson has turned into a very reliable free throw shooter(84.1%), him drawing fouls would only boost his production. Of course that assumes a defender can react to Johnson's quick fire shot or that he will seek contact which is not something he generally does. Johnson has also benefited from open looks generated by his teammates drawing the defense. If that continues, Johnson's FTR won't improve due to an absence of opportunity.
On the rebounding front, Johnson has been by far the best defensive rebounder of the group but at the same time the worst offensive rebounder. His DR% of 29.3 is well ahead of Zeller and Hansbrough and just above May. On the offensive end, Johnson is below 10% in offensive rebounding rate. The oddity here is Johnson has been a better offensive rebounder in the past. As a junior his OR% was 11.0 and as a sophomore it was 12.4. In that respect there is clearly room for improvement given he has done it before.
Johnson's biggest issue actually has nothing to do with his numbers. For the most part his numbers through 12 games are on pace with three of the best post players in the Roy Williams era. Unfortunately for Johnson, he is not perceived in the same light. There has been far too much talk over the years about consistency, effort and focus and that talk inhibits the ability to see Johnson as a great player. His struggles on the defensive end are also an issue as is the perception Johnson lacks toughness, especially against bigger, stronger interior players.
Of the three players listed with Johnson above, two of them were ACC Players of the Year and in Hansbrough's case, consensus national player of the year. May probably should have been ACC POY in 2005 but the award went to Duke's J.J. Reddick. The fact Johnson's numbers are in line with three ACC POY caliber players says something. If he can continue to put up these highly efficient games and also keep the traditional stats at a near double-double level, he is almost a lock for All-ACC and certainly in the discussion for the league player of the year award.