FORT WORTH, Texas (AP) — No matter how good quarterback Trevone Boykin and tailback B.J. Catalon looked at times, No. 15 TCU couldn't overcome the mistakes by the freshmen players — or the quick-strike big plays by Iowa State.
That was a bad combination for the Horned Frogs in their first Big 12 home game.
Iowa State led for good after a 51-yard pass on the fourth play of the game, the first of three touchdowns from Jared Barnett to Josh Lenz. The Cyclones went on to a 37-23 victory Saturday to end TCU's 12-game winning streak, the longest for a BCS team.
"We never played Trevone Boykin. Everybody acts differently with leadership and everything else. You gotta get used to it," coach Gary Patterson said. "You have to play B.J. Catalon. The guys we had problems with as far as turnovers hadn't played any games."
Boykin was 23 of 40 for 270 yards with a touchdown while starting in place of suspended quarterback Casey Pachall. But he threw three interceptions, one on his very first pass before two more in the fourth quarter.
The Horned Frogs (4-1, 1-1 Big 12) had planned to use Boykin at tailback this week before Pachall's arrest early Thursday for suspicion of driving while intoxicated.
Starting tailback Matthew Tucker had an ankle injury that kept him from playing after the Frogs had already lost leading rusher Waymon James three weeks ago to a season-ending knee injury.
With Boykin at quarterback, Catalon got 13 carries for 86 yards. But he had two fumbles, one inside the Iowa State 5.
The Frogs had won a nation-best 25 conference games in a row, the first 24 while winning the Mountain West championship each of the past three seasons. They won their Big 12 debut at Kansas three weeks ago, and hadn't lost a conference game since Nov. 6, 2008, at Utah.
"You can't give up big plays on defense and you can't turn the ball over on offense," Patterson said. "Real simple."
This is the third season in a row Iowa State (4-1, 1-1 Big 12) won on the road against a Top 25 team. And don't forget that double-overtime victory at home last year over Oklahoma State that cost the Cowboys a shot at the BCS national championship.
"I don't think they are so much upsets anymore," said Jake Knott, the senior standout linebacker who had a late interception. "There's a lot of people now that respect us on a new level. We need to keep winning games like this to do that."
Jaden Oberkrom had field goals of 38, 50 and 39 yards for TCU, which lost for only the second time its past 30 home games.
Pachall wasn't on the sideline after Patterson changed his initial decision to have the quarterback in uniform without playing.
The coach is scheduled to meet Sunday with TCU's chancellor to discuss Pachall, who eight months before his arrest this week admitted to police that he smoked marijuana and failed a team-administered drug test.
"Disappointing not have Casey. He's an experienced quarterback. He's been through the big games. But Trevone is the quarterback now. So we're standing behind him 100 percent," receiver Josh Boyce said.
"He's got to eliminate the turnovers. For his first start, we didn't the win, so it's not great. But he did pretty good."
Iowa State, which is home against No. 7 Kansas State next week, won for only the third time in 33 road games against a Top 25 team since 1996. All of those wins have come in the past three years in the state of Texas, including Barnett's first career start last season at Texas Tech.
"It feels great, but it doesn't mean nothing if we don't come back and finish strong the rest of the season," said Lenz, who had five catches for 147 yards.
Barnett was 12 of 21 for 183 yards and ran nine times for 30 yards in his first start this season. The TDs of 51 and 74 yards in the first quarter put the Cyclones up 16-7, and he threw a 1-yarder to Lenz to start the second half.
Despite temperatures in the 50s, Boykin was dealing with leg cramps. He stayed on the ground after rolling right and throwing a 28-yard pass to Brandon Carter early in the fourth quarter.
When Boykin returned for the next series, the 6-foot-7, 280-pound defensive end David Irving batted the ball and grabbed it out of the air, returning the interception 20 yards for a touchdown.
"It's going to be a long journey. It's not just going to be one year," said Patterson, who has already played 15 true freshmen. "I have a lot of young players. Until we threw the interception, it's a seven-point game."