AMES, Iowa (AP) — The quest for a spot in the College Football Playoff often includes some unexpected challenges.

For No. 4 TCU, that means a huge road game Saturday at Iowa State — yes, Iowa State — with first place in the Big 12 on the line.

The Horned Frogs status' as the Big 12's biggest surprise has been usurped by the 25th-ranked Cyclones (5-2, 3-1), who are in the Top 25 for the first time in 12 years.

Iowa State has vaulted into a tie for second in the league after stunning Oklahoma in Norman, throttling Kansas in Ames and stymieing Texas Tech in Lubbock.

TCU (7-0, 4-0) has been the class of the conference so far, winning its last two games over Kansas State and Kansas by a combined score of 69-6.

But it won't be easy for the Horned Frogs, especially with temperatures in the upper 30s, wind gusts of up to 30 MPH and even the possibly of snow showers in the forecast.

"Tough place to play no matter what kind of football team goes in there. You've got to be ready to go," TCU coach Gary Patterson said.

Here are some of the keys to consider as TCU and Iowa State prepare to face off in Ames for just the fourth time:

GETTING DEFENSIVE

This might be the rare Big 12 game in which the defenses take center stage. TCU and Iowa State are tied atop the Big 12 with just 61 points allowed through four conference games. The Horned Frogs are allowing a league-best 15.3 first downs a game, and the Cyclones lead with a turnover margin of plus-8. "The biggest thing about TCU is speed," Iowa State second-year coach Matt Campbell said about the Horned Frogs' defense. "They know what their answers are."

THE MAN ON THE HILL

TCU's revival following a 6-7 season in 2016 has come in large part behind the play of quarterback Kenny Hill. His 70.2 percent completion rate is fourth-best in the country, and he's thrown 15 TD passes with just three picks. But Iowa State's success on defense has come from giving opposing quarterbacks multiple looks, keeping plays in front of them and pouncing on mistakes, so Hill could find himself in trouble if he forces plays.

SPREAD OUT

One of the reasons Iowa State has been so successful this season is that it is loaded at wide receiver. The Cyclones have six receivers with at least 13 catches, led by senior Allen Lazard (33 receptions, 371 yards and 5 TDs). Iowa State also boasts one of the nation's best young backs in David Montgomery, who has rushed for 642 yards and eight TDs. "Everybody knows about Lazard. But they have 2 or 3 guys that can go, and they've got a running back that's hard to bring down," Patterson said.

KEY NUMBERS

TCU has a 30-2 record in the three seasons after a non-winning record in Patterson's 17 years in charge. ...Iowa State quarterback Kyle Kempt, a walk-on who has started the last three games in place of Jacob Park, has completed 69.7 percent of his passes this season. ... The Horned Frogs lead the nation in third-down conversion percentage (56.2) while ranking 10th in third-down defense.

HE SAID IT

"This team has never been like 'Let's just get to six wins and the season is over because we're going bowling' or whatever. We've set our goals way higher than that. We're trying to play for the Big 12 championship. We're trying to get ourselves in the playoff, play for the big time bowls, get a championship program going here," Iowa State linebacker Joel Lanning said.

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