Summers atoned in a big way, hitting a 3-pointer with 18.6 seconds left to lift the Spartans (No. 22 ESPN/USA Today, No. 19 AP) to a 67-63 win over the fifth-ranked Longhorns at the Toyota Center.
"I told him if he would just concentrate on doing his assignments, everything else would fall in place," Izzo said. "He's a good shooter. He is a big-time player. He's just got to do more things defensively. Today, he grew up a little bit."
Summers went 5-for-11 from the field and finished with 14 points. Goran Suton had 18 for the Spartans (8-2), who went 8-for-17 from the free-throw line and were outrebounded 37-34.
Suton was playing his second game since missing a month with a left knee injury. Izzo was hoping to get 15 minutes out of the 6-foot-10 senior, and got 26. Suton also had two rebounds and two steals.
"I've always questioned his toughness a little bit," Izzo said. "This kid reached down. He gave everything he had."
Gary Johnson scored a career-high 20 for Texas (9-2), and gave the Longhorns a 63-62 lead on a driving layup with 1:30 remaining.
Summers drove into the lane and lost the ball to Connor Atchley on Michigan State's next possession. Justin Mason missed a 3-pointer and the ball went out of bounds with 29.8 seconds left, giving the Spartans a chance to set up the final play.
Raymar Morgan took the inbound pass and found Summers open on the wing for a 3-pointer, his second of the game. Abrams mishandled a pass from Mason near the Texas sideline, giving the ball back to Michigan State with 13 seconds left.
The Longhorns finished with 15 turnovers. Mason had gone 18 consecutive assists without committing a turnover before the late miscue.
"They're a very good defensive team," said Texas coach Rick Barnes. "They made it hard to score."
Michigan State's Kalin Lucas missed the front end of a 1-and-1, but Mason missed a 3-pointer at the other end. Summers ended up with the ball and hit two free throws with 0.1 seconds left.
Abrams, who averaged 28.5 points over his previous four games, went 3-for-10 from the field and scored eight points. He went 0-for-4 from 3-point range, failing to hit one for the first time this season.
Michigan State's Travis Walton shadowed Abrams most of the game, but the Spartans' defense seemed to follow him wherever he went. That gave Johnson more scoring opportunities, but the Spartans seemed content to focus on Abrams, the Longhorns' leading scorer.
"Every time I did catch the ball, if I did catch the ball, I was kind of out of position," said Abrams, who came in shooting 47 percent from 3-point range. "They just did a good job on me. Looking back on it, if I could do something different, I might kind of slow down a little bit."
The game got off to an ugly start, with the teams combining to miss 11 of their first 14 shots and giving away six turnovers in the first five minutes. It was testy, too -- Texas forward Damion James and Walton faced off and jawed at each after fighting for a rebound.
James scored eight straight points for Texas, including a three-point play that put the Longhorns up 15-8.
Near the 10-minute mark, Mason ran into a screen by Michigan State's Idong Ibok and hit the floor. He went to the locker room holding an ice pack against the right side of his face.
The Longhorns kept their slim lead by controlling the boards, and the Spartans helped by missing their first five free throws. Michigan State came in shooting 65 percent from the free-throw line for the season and Izzo admits its a team weakness.
"We're going to have to spend more time on it," Izzo said. "Free-throw shooting is like throwing strikes, or a quarterback who can't hit open people. It gets in your head. It is a problem. I don't feel like we're Memphis, and we can overcome it. We have to be better at it."
But Michigan State trailed only 34-32 at the break after holding Abrams to four points on 2-for-6 shooting.
Mason started the second half wearing a bandage over his right eye. He took six stitches for a cut, school officials said.
Atchley, who didn't score in five minutes in the first half, sank two 3-pointers a minute apart to give Texas a 47-42 lead. Suton's 3-pointer at the 12-minute mark to cut the lead to two. Suton was playing his second game since missing a month with a knee injury.
The Longhorns rebuilt the lead to 61-56 before Lucas hit a free throw, Summers sank a 3-pointer from the corner and Lucas hit a short jumper to put the Spartans up by one heading into the final three minutes.