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Keep the bus running and point it toward St. Louis. Thanks to a jaw-dropping comeback, Illinois' journey has another leg left: the Final Four.

Trailing 75-60 with four minutes left, Illinois showed why it was No. 1 most of the season.

With Deron Williams leading the way, the Illini staged an electrifying and improbable comeback to force overtime and then held on to beat Arizona 90-89 Saturday night to win the Chicago Regional.

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The Illini (36-1), who've been able to drive to their two tournament sites in Indianapolis and suburban Chicago so far, can keep on busing.

In St. Louis, they will play Louisville (33-4), which rallied from a 20-point deficit Saturday to beat West Virginia 93-85 in overtime and take the Albuquerque Regional.

The last time two regional final games went into overtime in the same year was 1992 when Michigan beat Ohio State, and Duke eliminated Kentucky.

Williams tied the game and capped a stunning 20-5 run by hitting a 3-pointer with 38 seconds left in regulation, making it 80-80.

Arizona (30-7) went up by 15 points after an 18-6 spurt that momentarily silenced a large orange-clad partisan crowd.

But the Illini didn't play like it was over. And it wasn't.

Illinois, whose previous largest deficit this season was nine, made a final run and it was a great one.

Luther Head hit a 3-pointer, Dee Brown made a basket in the lane, Head scored after a steal, Williams drove for a basket and then made a steal and fed Brown for another basket with 45 seconds left.

After Jack Ingram deflected an inbounds pass, Williams hit a 3-pointer to tie it with 38 seconds to go.

Salim Stoudamire, the hero of Arizona's semifinal win over Oklahoma State, dribbled the clock down and then passed the ball to Jawann McClellan. He missed but Stoudamire came up with the rebound, only to have his shot blocked by Head.

Williams hit two more 3-pointers in overtime, but Illinois' victory wasn't secured until Arizona's Hassan Adams, who'd scored five points to get the Wildcats within a point, missed a shot just before the final buzzer.

Illinois' players then swarmed the floor in celebration of the school's first Final Four trip since 1989.