Williams scored 11 points in his first game back after being sidelined by a groin injury, but the Jayhawks grabbed control at the start of the second half and went on to a 60-46 victory on Saturday.
"I felt like we got too comfortable," Williams said. "They noticed we got comfortable and that when we took the first punch."
Williams, who missed the previous two games, was 3 for 7 from the field and 5 for 6 from the free-throw line while playing 31 minutes. He also had two steals and two assists.
"He had to play more and he was hurt," Texas Tech interim coach Chris Walker said. "For the most part I was happy with his energy level. He really took it upon himself. He really wanted to guard (Ben) McLemore and he did a really good job of that."
McLemore scored 33 points to lead Kansas to a 97-89 overtime win against Iowa State in the Jayhawks' previous game. The freshman averages 16.9 points but only managed 10 against the Red Raiders.
But McLemore got plenty of help.
Kevin Young scored 14 points for Kansas (14-1, 2-0 Big 12), which has won 13 in a row. Jeff Withey and Travis Releford had 12 points apiece.
Williams made three free throws with 5 seconds left in the first half to trim Kansas' lead to 27-25 at the break. Dejan Kravic then made a foul shot at the beginning of the second half to get the Red Raiders within one.
Kansas responded with a 14-2 run to open a 41-28 lead with 13:41 remaining. Young started the spurt with a layup and Releford closed it out with two free throws.
Kravic had nine points and eight rebounds for the Red Raiders (8-6, 1-2), who shot 35 percent from the field and committed 16 turnovers.
Releford got back-to-back steals during a 12-3 run late in the game. On one, he fed Young for a layup and on the second one he outraced his defender and dunked to put the Jayhawks up 58-40.
Red Raiders reserve Jaye Crockett, who averages 14.8 points, was held to three points on 1-of-8 shooting. He made a 3-pointer with 1:21 left in the game.
The Jayhawks continued their pursuit of a record ninth straight Big 12 title. Kansas has won six outright championships and twice shared the title with Texas, in 2006 and '08—the year the Jayhawks won the national title.
Kansas went 16 for 18 at the line in the first half. It was the Jayhawks' lowest scoring first half of the season.
The Red Raiders scored five of the final six points of the half, including Williams' foul shots after he was fouled by Elijah Johnson while attempting a 3-pointer.