By JOHN MARSHALL AP Basketball Writer

An unprecedented day of chaos led to changes nearly everywhere in the AP Top 25, except the top two spots.

It also tightened up major conference races across the country.

Heading into the final week of the regular season, the first-place team in every undecided league except the Pac-12 has a lead of one game or less. The Pac-12 hasn’t been decided, either; No. 2 Arizona leads No. 16 Southern California by 1 1/2 games, but has three games this week.

In the Big East, No. 9 Providence clinched the regular-season title over the weekend.

To say it’s going to be a big week in the AP Top 25 is an understatement.

ACC

No. 4 Duke will play one of the biggest games in Cameron Indoor Stadium history on Saturday. Not only is it against North Carolina, it will be the final home game in the storied career of coach Mike Krzyzewski.

It could decide the ACC regular-season title, too.

The Blue Devils (25-4, 15-3, ACC) moved up three spots in this week’s poll and gave themselves a one-game lead over Notre Dame by beating Syracuse on Saturday.

Duke also plays at Pittsburgh on Tuesday in its bid to win the ACC regular-season title for the first time since 2010.

The Irish play Florida State on Wednesday, Pittsburgh on Saturday.

BIG 12

No. 3 Baylor took a big step in tightening the Big 12 race with its 80-70 win over No. 6 Kansas on Saturday. The Bears, who climbed seven spots in Monday’s AP Top 25, then took over the conference lead by a half-game with Monday night’s 68-61 win over Texas.

Baylor hosts Iowa State on Saturday.

Kansas (23-5, 12-3 Big 12) has three games left in its bid to win at least a share of its 20th Big 12 title in 26 years. The Jayhawks play TCU, which beat No. 12 Texas Tech last week, in consecutive games and close out the regular season at home against Texas on Saturday.

Texas Tech is 1 1/2 games back of Baylor after beating Kansas State on Monday night and closes the season against Oklahoma State on Saturday.

BIG TEN

While seven of the top 10 teams lost on Saturday, No. 10 Wisconsin (23-5, 14-4 Big Ten) kept its hold on the Big Ten lead with a win against Rutgers.

The Badgers lead by a game over No. 8 Purdue and No. 20 Illinois, but face a huge test against the Boilermakers on Tuesday. Wisconsin closes out the regular season at home against Nebraska on Sunday.

No. 8 Purdue (24-5, 13-5) missed out on a big opportunity in Saturday’s chaos, losing to Michigan State 68-65. That dropped the Boilermakers seven spots in this week’s poll and potentially off the No. 1 seed line in the NCAA Tournament.

Purdue finishes the regular season Saturday at home against Indiana.

Illinois (20-8, 13-5) hosts Penn State on Thursday and No. 24 Iowa Sunday.

PAC-12

No. 2 Arizona cost itself a shot at securing at least a share of the Pac-12 regular-season title with its lackluster loss at Colorado on Saturday.

The Wildcats (25-3, 15-2 Pac-12) still have 1 1/2-game lead in the conference, but face a tough makeup game at Southern California on Tuesday. Arizona closes out the regular season at home against Stanford on Thursday and California Saturday.

The Trojans (25-4, 14-4) end the regular season against No. 17 UCLA in a rivalry game Saturday.

SEC

The SEC has a four-team race going down to the wire.

No. 13 Tennessee (21-7, 12-4, SEC) tightened things up on Saturday by beating No. 5 Auburn 67-62.

The Tigers (25-4, 13-3) lead the Vols, No. 7 Kentucky and No. 14 Arkansas by a half-game. Auburn closes out the regular season with road games against Mississippi State and South Carolina.

The Wildcats (23-6, 12-4) play Ole Miss and Florida. The Razorbacks (23-6, 12-4) face LSU and close out the regular season against Tennessee, which also has a game against Georgia.

Auburn clinches with two wins this week, but things could get complicated if it loses either one. 

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