TCU ended its run in the Mountain West last season with a league-record 17 consecutive home wins.

Coach Gary Patterson's young team now gets its first chance to protect its home field against a Big 12 opponent.

The 15th-ranked Horned Frogs look to extend the nation's longest active winning streak to 13 on Saturday when it faces Iowa State.

After winning its third consecutive Mountain West title last season, TCU (4-0, 1-0) is off to a quick start in its first season in the Big 12. With a 20-6 victory over Kansas on Sept. 15, the Horned Frogs have a 25-game unbeaten streak in conference play.

Patterson, though, is having a hard time gaging where his squad is at through four weeks, saying "it depends on the day," whether his team is a good one. He is disappointed with the 25 penalties in the last two games - playing 15 freshman has played a big part in that - but the driving rainstorm his team played through in last Saturday's 24-16 win at SMU also made it difficult to provide a proper analysis.

"Is the defense as good as the 2008 defense (that was best in the nation)? No. Has the offense played as well as the Rose Bowl offense (that was 12th in the FBS in 2010)? No. But the key to it is on the games that you have to, we've been better," Patterson said.

The offense has plenty of room for improvement behind junior quarterback Casey Pachall, who threw two touchdown passes and went 10 for 26 for 107 yards last Saturday when the Horned Frogs totaled a season-low 156 yards.

TCU had three points and 27 total yards following halftime.

The Horned Frogs, though, are one of the nation's best defensive teams, ranking second in the FBS in scoring defense at 7.25 points per contest and seventh with 255.8 yards allowed per game.

TCU is also tied for second in the nation with nine interceptions after picking off five passes last weekend.

"I knew the defense was going to have to step up,'' safety Elisha Olabode said after intercepting his second pass this season.

Freshman end Devonte Fields has definitely stepped up, leading the Big 12 with five sacks and 8 1/2 tackles for loss.

Facing Fields and a TCU team with 11 sacks - second in the league - the Cyclones (3-1, 0-1) will have to do a better job protecting senior quarterback Steele Jantz than last Saturday when he was sacked four times in a 24-13 loss to Texas Tech. Jantz was facing one of the best defensive teams in the nation in that game, but he still needs to improve after completing 10 of 20 passes for 73 yards and a career high-tying three INTs.

Iowa State totaled 189 yards in the loss and is 88th in the FBS in total offense (369.0 ypg) and scoring (24.3 ppg).

"We're concerned - we scored six points (on offense) and we're under 200 yards," coach Paul Rhoads said.

But like TCU, the Cyclones have received standout defensive performances. Led by senior linebackers A.J. Klein, who tied the NCAA record with four INT returns for a touchdown by a linebacker with his 87-yard score last Saturday, and Jake Knott, Iowa State is yielding 14.0 points per game - 17th-best in the FBS.

"Those kids played good defense and they know it, and they did it against a squad full of talented offensive players," Rhoads said after his team held the Red Raiders to season lows in points and rushing yards with 63. "That maturity, along with that level of play - the best level of play we've played at in four years - leaves them hungry for more. I think there's a great desire to keep playing great defense against offenses that are obviously the best in the land."

The Horned Frogs wouldn't be considered as one of those, but the Cyclones' secondary still needs to keep an eye on wide receivers Brandon Carter and Josh Boyce, the program leader with 18 TD receptions, who have combined for 540 receiving yards and seven scores.

Pachall needs two TDs to move past Casey Printers for third at TCU with 38.

The Horned Frogs are 3-0 all-time against Iowa State after winning 27-24 in the 2005 Houston Bowl.

In the Cyclones' only previous visit to Fort Worth in 1995, TCU posted a 27-10 victory.