The 6-foot-5, 220-pound sophomore is playing at the 4-spot against bigger players and leading the team in scoring since the lineup change.
"I don't want to say I'm the reason, but I'd say I have something to do with it because of the lineup change," Hairston said. "Any person can change the face of a game. ... I'm not the one that's causing us to win because we're playing as a team and we're playing together. That's what's helping us win."
Hairston is right about the team's overall improved play, but so much of that flows from Hairston's bigger role. His ability to knock down the outside shot spreads the floor to open driving lanes for fellow sophomore James Michael McAdoo and senior Dexter Strickland, while also giving perimeter defenders another concern other than 6-7 junior Reggie Bullock.
Quite simply, the move has changed everything for the Tar Heels, not to mention given UNC some optimism for what lies ahead after a bumpy first half of the season. North Carolina has already clinched a top-four seed and a first-round bye in next week's ACC tournament in Greensboro, and could tie the Blue Devils (26-4, 13-4) for second behind Miami.
"He should get a lot of credit," freshman point guard Marcus Paige said. "He's always had the potential to be a big-time player for us and he took full advantage of his opportunity when coach decided to expand his role a little bit and put him in the starting lineup and try to get something going for us.
"Obviously that something got going really well with P.J., and he's been playing like a first-team all-ACC player ever since he got put in the starting lineup."
Duke's Mike Krzyzewski can see it, too.
"Hairston's played great," the coach said. "I mean, not good, he's played great. He's taken advantage of his matchup and that matchup hasn't taken advantage of him because he's a really tough kid. He's strong. I just think he's tough-minded. ... Really he's been one of the best players in the conference these last few weeks."
Before the switch, Williams was starting sophomore center Desmond Hubert to give the Tar Heels size, defense and rebounding. Hairston provided the offensive punch off the bench.
The Tar Heels had played with the four-guard lineup occasionally before the decision to go with it full-time began in the aftermath of the blowout loss at Miami on Feb. 9.
"We got killed, and I'm sitting in the locker room and I've got to do something," Williams said. "That was the bottom line. And I had already thought about it some but I didn't get any crystal ball or anything. ... It just seemed like the right thing to do at that time."
In the last seven games, Hairston is averaging a team-best 17.6 points, four points than his season average. He's scored in double figures every game since becoming the starter, first matching his career-high with 23 points in Duke's Cameron Indoor Stadium then besting that with 29 at home against Virginia.
Along the way, Hairston has matched up with preseason ACC player of the year C.J. Leslie of North Carolina State (who stands 6-9) and figures to get another tough matchup Saturday with Ryan Kelly. Kelly, a 6-11 senior who can stretch defenses with his own outside shot, returned to the lineup last weekend from a foot injury that sidelined him two months and scored a career-high 36 points against the Hurricanes.
"I feel like I'm up for the challenge," Kelly said. "He's been playing very well, their whole team has. They're talented and they're hot right now, and it's going to be a test. But ... you have to take advantage of what they're giving you: get in the post, get in deep position in the post, finish around the basket, get to the offensive boards. I'll be playing my game."
That's one reason why Williams has pushed Hairston to learn to defend from in front of post players as part of his crash course to playing the 4. The coaches have also stayed on Hairston to stop kicking out his right leg on his jumper and improve his balance, with first-year assistant Hubert Davis even sending clips of NBA sharpshooter Ray Allen to Hairston over the summer as an example.
There's no arguing with the results, whether for Hairston individually or the Tar Heels.
"It's just a matter of we have to keep doing it from here, like we finally realized who we can be and what we can do," Hairston said. "We finally put it together and brought it to the court."