CHAMPAIGN — Purdue is the toughest place in the Big Ten for a visiting team to have to play. Just ask the conference’s coaches, nearly all of whom said so in a preseason survey conducted during media days in Rosemont.

Yeah, well, do you know where else it’s no damn picnic at all to go on the road and lace ’em up?

You already guessed the answer. On a bonkers Friday night at State Farm Center, Illinois came back to beat the No. 18 Boilermakers 88-80, ending a five-game losing streak in the series. There can’t have been a louder gym all season. We’re just going to have to call it a tie for first with wherever else.

The Illini (20-11, 12-8 Big Ten) trailed 63-53 with nine minutes gone in the second half. Fans were going ballistic because of a phantom foul called on guard Kasparas Jakucionis, who was whistled by official Randy Richardson for nipping Fletcher Loyer on a block of a three-point attempt that couldn’t have been cleaner had Jakucionis been wearing surgical gloves. Richardson and Underwood then got nose-to-nose in a tense confrontation, with Underwood being pulled back by assistants.

With a huge assist from the crowd, the Illini took over from there, going on a 17-3 run sparked by freshman Will Riley, who scored 22. Tre White, who had 20, tied it at 63-63 with a three. A Ben Humrichous three gave the Illini their first lead in 23 minutes of game time.

Jakucionis — in what likely was his final home game — hit a step-back three with 40 seconds left for an 82-79 lead. The roof almost blew right off the joint in the regular-season finale for both teams. Purdue (21-9, 13-7) was all out of answers.

The Big Ten tournament in Indianapolis — and then the NCAA Tournament — awaits both teams. The Illini will be hoping for the return of freshman big man Morez Johnson Jr., whose interior defense and overall physical presence has been missed as he recuperates from a broken left wrist. Johnson was without a cast for the first time Friday. He’ll be fitted for a brace and could play as soon as Thursday, the Illini’s next time out.

Illinois hit its magic number — 80 — moving to 19-1 this season when scoring at least that many points. The record is 1-10 when the Illini don’t get there, something to keep in mind going forward.

Illinois also joined Houston, Gonzaga and San Diego State as the only programs in the country with at least 20 wins in each of the last six seasons. Over those six seasons, Purdue and Illinois are tied with 81 Big Ten wins, leading all schools.

And Underwood? Well, he’s still stuck on 99 losses in his nearly eight full seasons here. Might as well keep avoiding triple digits for as long as possible.

This was a big win for a team that hasn’t finished certain games against top opponents well. Purdue point guard Braden Smith, whom Underwood likens to John Stockton, dominated the first half, most of which was a layup line for his team. But Riley — Underwood calls him “Tyrese Haliburton-like” — was great. Others rallied behind him.

That included all the orange-clad maniacs in the stands. Mackey Arena can’t do it any better than they did.

• THIS ILLINOIS TEAM was a total rebuild by Underwood and his staff, with only one player on the roster — reserve Dra Gibbs-Lawhorn — who had anything to do with last year’s run to the Elite Eight. But who will be back next season? In today’s game, no one ever knows.

“Will somebody unexpectedly leave? Probably,” Underwood told the Sun-Times this week. “Don’t know who, what. It’s just the way it is.”

Jakucionis is a projected lottery pick, and classmate Riley another strong contender for the first round. But much of the team could return — potentially including 6-9 shooter Humrichous, who was part of Friday’s Senior Night. As a former NAIA player, Humrichous can seek a waiver for one more year of eligibility. Underwood seemingly hopes to have him back. …

• NOBODY WANTS A PIECE of Michigan State right now. The Spartans have won six in a row and will take the Big Ten by a full three games if they win at home Sunday against Michigan. Oregon also has won six straight and — with a layup against awful Washington still to go — should arrive in Indy on a seven-game tear. …

• GAMES OF THE WEEKEND: No. 6 St. John’s at No. 20 Marquette (11 a.m. Saturday, Fox-32), No. 7 Alabama at No. 1 Auburn (1:30 p.m. Saturday, ESPN), Ohio State at Indiana (2:45 p.m. Saturday, ESPN), No. 2 Duke at North Carolina (5:30 p.m. Saturday, ESPN), No. 17 Michigan at No. 8 Michigan State (11 a.m. Sunday, Ch. 2).

Rick Pitino’s hottest-in-the-land St. John’s squad has lost once — once! — since New Year’s Eve. UNC can sew up an NCAA berth with an upset of its soaring rival. The bubble pressure faced by both OSU and — especially — Indiana is off the charts.

• MY LATEST AP TOP 25 BALLOT: 1. Auburn, 2. Houston, 3. Duke, 4. Tennessee, 5. Florida, 6. St. John’s, 7. Michigan State, 8. Alabama, 9. Texas Tech, 10. Clemson, 11. Iowa State, 12. Wisconsin, 13. Maryland, 14. Louisville, 15. BYU, 16. Memphis, 17. Michigan, 18. Missouri, 19. Marquette, 20. Purdue, 21. Kentucky, 22. Arizona, 23. Saint Mary’s, 24. VCU, 25. UConn.