LOUISVILLE, Ky. -- On Dec. 19, 2018, Purdue was an unranked 6-5 team staring down a five-game stretch on its schedule that would come to feature four 2019 NCAA Tournament squads. 

The Boilermakers' only win vs. 2019 NCAA tourney competition at that point came by just two at home against a Maryland team that itself wouldn't win a game against a tournament team until Jan. 8.

Purdue's brutal strength of schedule was legitimate -- three of the losses came to Sweet 16 programs (Virginia Tech, Florida State and Michigan) plus a four-point road defeat at Texas -- but the team was limping as it was twisting. As coach Matt Painter said on Friday, Purdue's warts were exposed at that point.

The players knew the season hinged on that Christmastime stretch.

"In the middle of December, late December, we had a moment where we started to realize, we've really gotta start playing well if want to make the tournament, because right now we're playing ourselves out of it," Purdue junior guard Carsen Edwards told CBS Sports.  

But the Boilermakers won four out of those five games and rescued this remarkable season.

But before that stretch, the languor was expected. This 2018-19 Purdue crew featured the biggest roster flip of Matt Painter's coaching career. This season was only the second time he lost as many as four starters from the year prior -- and in fact the 41 total starts from a season ago is the lowest year-to-year change Painter ever faced.

The previous time, in 2012-13, Purdue finished 16-18. Though Edwards was a consensus preseason First Team All-American, the lack of proof around him was why, in my annual preseason ranking of every team in college basketball, I slotted Purdue 44th despite the fact it won 30 games and made the Sweet 16 last season. 

Purdue lost starters Vincent Edwards, Isaac Haas, Dakota Mathias and P.J. Thompson, who collectively accounted for approximately 49 points, 19 rebounds and nine assists per game. Minutes-wise, the drop-off was huge. Recruiting-wise, Purdue's 2018 class ranked ninth-best ... in the Big Ten. 

Here's what I wrote about Purdue back in October:

Carsen Edwards rightfully is demanding a lot of pub for Purdue this season, but Evan Boudreaux is a transfer from Dartmouth who could be the boost Purdue needs to get back to the NCAAs. I'm fascinated by what Purdue could be, as 7-3 center Matt Haarms, who has arms like helicopter rotors, should be vastly improved. Underrated senior: Ryan Cline. Breakout candidate: Nojel Eastern. OK, so why do I have Purdue 44th? That's the thing: I don't know.

Maybe listen to your instincts next time, idiot. 

Purdue's March shooting -- most of it from Edwards and Ryan Cline -- has made history. The Boilers sank 15-plus 3-pointers in back-to-back NCAA tourney games, becoming the first team ever to do that. They shot a combined 31 for 61 from beyond the arc vs. Villanova and Tennessee

"I think we've got better players than what people give us credit for," Purdue assistant Greg Gary told me on Friday. "Paint, the whole year, didn't talk about last year. I can't even tell you -- we'll watch film of a previous opponent we've played [the year before] but he never talks about last year. At all. I think that's some of it. We're in the present."

There were no players-only meetings or come-to-Jesus moments for the coaching staff. It was patience and trust and players truly understanding their roles. Instead of thinking they could win and barrel through teams based on the force of their offense, Purdue's players tightened defensively.

Purdue coach Matt Painter instructs his team in Thursday's Sweet 16 win vs. Tennessee. USATSI

"We weren't guarding anybody very well," Gary said.

They've gotten noticeably better. Purdue ranks 28th in defensive efficiency at KenPom, outperforming last year's pace. The dramatic 99-94 OT win against Tennessee got the Boilermakers to 26 wins, bringing them company with huge names as one of just six schools to notch 26 victories or more the past four seasons; Villanova, Kansas, North Carolina, Gonzaga and Kentucky are the others.

The talent is underrated and the coaching staff is still underappreciated by too many.

"Coach Paint works like an assistant as far as his evaluations of kids that are coming in," Gary said. "He will see guys as much, sometimes more than we do as assistants, during the year. There's no question it's part of why he's been successful, because he's seeing what he's getting and knows what he's getting."

Painter's reputation as a patient, instinctive, modern-thinking coach has been well-established. He subtly made moves -- 7-foot-3 center Matt Haarms has started 23 of 35 games this season -- and the team built up its confidence and didn't falter despite Edwards hitting multiple shooting slumps. 

Now it's the opposite. Edwards is torching.

Much has rightfully been made of Edwards becoming the first player since Stephen Curry to score 25 or more points in four consecutive NCAA Tournament games, but the truth is the bulky junior is a flawed-but-fun flamethrower. He takes tough shots, makes tough shots -- and the tough takes aren't as abundant now as they were earlier this season and last, which has been significant. 

"The other guys on the team being mature about it and not being petty or jealousies or any of that stuff, the other guys around Carsen did a phenomenal job of accepting it," Gary said. "It's really that simple. If there's any jealousies or any issues, it's going to come out."

They haven't. Edwards' ups and downs haven't been the barometer for Purdue, which is something few would have thought realistic back in November.

"When Carsen struggled shooting, we were still winning road games," Painter said. "When we had other breakdowns, different guys would step up and win games for us. I thought those were good signs from there. But no, we really just kind of stayed with our same group for the most part and just tried to keep getting better together. I didn't think it was our personnel. Sometimes we shoot the ball too quick and we've just got to be more patient."

It's not common for teams to lose four starters and retool for Elite Eight runs. It's not rare, either. Duke, Kentucky and Texas Tech all fit that description this season. The difference with Purdue is it doesn't have one player absolutely guaranteed to be drafted. Even TTU has a surefire top-10 pick in Jarrett Culver. 

To describe what Painter and his staff have pulled off as serendipitous would be to sell the players and the staff short. Purdue has rated as a top-10 team in KenPom dating all the way back to Jan. 23, when it was a 13-6 team. The predictive metrics told an accurate forecast. And through three tournament games, Purdue has the best case for being as dynamic and adaptive as any team left in the field. It won slow vs. Old Dominion, won with flair against Villanova, and won in about five different ways against a top-10 team in Tennessee. 

Now, poetic symmetry: Purdue will play top-seeded Virginia late Saturday night. Purdue's last Elite Eight appearance came in 2000, which ended in a loss to Wisconsin -- coached by Tony Bennett's father, Dick. If Purdue is going to break through, it will have to do so under the hardest road possible, by playing the highest available seed. 

That seems just right for this team, this season, this tournament.