NORMAN, Okla. -- Iowa State coach Paul Rhoads knew exactly what happened.
His Cyclone team was playing well, had Oklahoma in some trouble, too, but then Jalen Saunders shook loose for a 91-yard punt return for a touchdown which woke up the Sooner offense in what turned out to be a 48-10 victory at Owen Field.
"All of sudden something like that goes so wrong," Rhoads said. "We had the guy surrounded and he escapes and makes a great play."
The return with only 1:09 before halftime tied the game, 10-10, and after the Sooners got their running game going in the second half, it wasn't much of a contest.
"Jalen ignited us," coach Bob Stoops of Oklahoma said. "Fortunately, we made some positive adjustments in the second half. We tightened things up and executed in a better way."
Oklahoma ran for 209 yards in the third quarter after a first half in which it managed only six first downs.
The Sooners went on to score 38 points in about 22 minutes but it was the punt return after another bad first quarter that turned things around.
"The punt return was huge," Oklahoma center Gabe Ikard said. "For him to return that got things rolling. That was a giant play."
Running back Damien Williams scored on the second play of the third quarter on a 69-yard run, Brennan Clay added a 63-yard run and the Sooners added a field goal for a 17-0 quarter.
The Sooners finished the game scoring 41 points in a row.
Trevor Knight, who replaced starting quarterback Blake Bell in the second quarter after Bell sustained what looked like a head injury, ran for a 56-yard touchdown run on the first play of the fourth quarter.
Trainers took away Bell's helmet later in the second quarter, but he stayed on the sideline the rest of the game. Bell's status for next week is unknown, but Knight probably will be the starter.
Knight started the season as the Sooners' quarterback, but was injured in the third quarter of Oklahoma's second game. He missed the next game because of the leg injury, but never returned as the starter.
"We knew he wanted to run more than he wanted to pass," Iowa State linebacker Jeremiah George said. "I just think somebody wasn't in the right gap."
Knight completed 8-of-14 passes for 61 yards, but his legs made the difference. Knight ran for 123 yards on 10 carries.
"His ability to get to the perimeter is a factor," Stoops said. "What it does is press the defense to be correct. If not, something pops in there."
It popped quickly for the Sooners in the second half and No. 18-ranked Oklahoma improved to 8-2 overall and 5-2 in the Big 12 Conference. Iowa State is 1-9 and 0-7.
In the first half, both Knight and Bell struggled.
Oklahoma had 25 yards of offense on nine plays in the first quarter and finished the first half with only 110 total yards, including 44 passing.
The Sooners have struggled in the first quarter and have yet to score a touchdown in the first 15 minutes of any game.
Iowa State got out to a 7-0 lead on Sam Richardson's four-yard touchdown run with 14:18 to go in the second quarter. The teams traded field goals before Saunders went for his touchdown run.
Oklahoma had 523 yards of offense, including 405 on the ground. Iowa State had only 291 yards of offense and ran for 103, including 50 on 13 carries by Aaron Wimberly.
NOTES: The Sooners averaged 9.2 yards per carry on 44 rushes, going for a total of 405 yards. ... Iowa State quarterback Grant Rohach completed 21-of-32 passes for 179 yards, with two interceptions. ... The Cyclones scored on consecutive possessions in the first half, getting a touchdown and a field goal. One possession ended at halftime and the next six ended in punts, with none of the drives lasting more than six plays. ... Oklahoma honored its seniors Saturday. Senior running back Damien Williams ran for a game-best 128 yards and two touchdowns. Senior Roy Finch had a season-high 10 carries for 45 yards.