EAST LANSING, Mich. -- Early in overtime, after a call went against his team, Texas Southern coach Mike Davis wandered down to the end of the bench, sat down and began joking with some Michigan State fans a few feet away.
One of the most shocking victories in school history was at stake, and Davis and his players were determined to enjoy themselves.
"It's really important for them to see me loose and having fun," Davis said. "I can get upset sometimes, and it kind of makes them nervous, and so I try to make sure that no matter what happens, I move to the next play."
Chris Thomas scored 22 points, and Texas Southern became the latest unheralded team to surprise a Big Ten school, beating No. 25 Michigan State 71-64 in overtime Saturday. The Tigers were coming off a 40-point loss to Gonzaga, but they remained poised throughout against the Spartans. Texas Southern never trailed in the extra session.
The Tigers (2-8) had not beaten an AP Top 25 team since a win over 16th-ranked Minnesota on Dec. 21, 1994, according to STATS.
"We did know it was possible as long as we stayed as a team," Thomas said. "We've played good teams before. We knew we were getting better."
Michigan State fans were giddy after rival Michigan was upset by the New Jersey Institute of Technology on Dec. 6, but now it's the Spartans who must deal with the aftermath of an almost unthinkable defeat. It's another tough result for the Big Ten this December. Nebraska lost at home to Incarnate Word less than two weeks ago.
Michigan State coach Tom Izzo said he didn't have his team prepared for Texas Southern.
"As you get older, you start worrying about people liking you, and I did not work my team. I felt sorry for them. I did not work them like I normally do," Izzo said. "We didn't practice as hard -- too worried about my little guys getting tired. ... That was a coaching loss, and I take full responsibility for it, and I plan on rectifying it starting at 8:30 tomorrow morning."
The Spartans (8-4) were without starting forward Branden Dawson, who fractured his wrist in a win over Eastern Michigan on Wednesday. Michigan State needed a free throw by Javon Bess with 6.8 seconds left in regulation just to force overtime.
The Spartans came in leading the nation at 44 percent from 3-point range, but they went 4-of-21 against the Tigers, who represented the Southwestern Athletic Conference in last season's NCAA tournament. Texas Southern had endured predictable struggles against a tough nonconference schedule in 2014-15. The Tigers lost by 19 to Indiana, by 12 to Tennessee, by 26 to Baylor and by 25 to Florida.
Then came the rout against Gonzaga -- and there was no indication that the Michigan State game would be any different.
But belief began building in the second half, when the Texas Southern bench started yelling its approval of every key basket -- while the Michigan State crowd tried to process what was happening.
In the final seconds of overtime, with the Tigers still shooting free throws to finish off the game, a couple Texas Southern players posed on the sideline for what looked like a picture or a video.
The Spartans led 30-25 at halftime, and after the Tigers tied it early in the second, Michigan State seemed to assert itself. But after Denzel Valentine's 3-pointer gave the Spartans a 50-42 lead, Texas Southern went on an 11-2 run and took a 53-52 advantage on Jason Carter's 3-pointer with 1:26 remaining.
The Tigers were up one when Bess came up with an offensive rebound and was fouled in the final seconds of regulation. A freshman playing only his second game, Bess made one of two free throws to tie it at 55.
Texas Southern regrouped and scored the first four points of overtime, and Michigan State's anemic shooting day continued. The Spartans didn't make a field goal in overtime until the final minute.
Michigan State paid Texas Southern $95,000 for Saturday's game, a Tigers official confirmed to ESPN's Darren Rovell.
Texas Southern turned the ball over only 11 times and shot a season-best 53 percent from the field. The Spartans did not do much to push the pace or fluster the Tigers.
"It means a lot, but we're not done yet," Thomas said. "We've got to win a lot more games to get to the tournament. It doesn't stop here."
Malcolm Riley scored 20 points for Texas Southern.
Izzo made it clear the Spartans will be working hard before their next game.
"I'm going to find out what the NCAA will legally allow me to practice tomorrow, and then I'm going to probably exceed it," he said.
Texas Southern: This was the first game all season for the Tigers that was decided by single digits. Their only previous win was 71-59 over Lamar on Nov. 28. That was also their only home game so far.
Michigan State: The Spartans had 18 offensive rebounds, but they were outscored 36-32 in the paint.
Texas Southern plays at Auburn on Tuesday night.
Michigan State hosts The Citadel on Monday night.
The Associated Press contributed to this report.
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