FORT COLLINS, Colo. (AP) -The top defense in the nation was slow to arrive but quick to recover Saturday, leading TCU past Colorado State 13-7 on a chilly afternoon at Hughes Stadium.

The Rams marched right down the field for a touchdown on their first possession, then could hardly find any holes to run through or yards to gain after the catch - when they did manage to hold onto the ball.

TCU (6-1, 3-0 Mountain West) ruined the Rams' homecoming and handed Colorado State (3-3, 1-1) its first home loss in six games dating to last year.

After its only airplane trip in a two-month span, the Horned Frogs looked like they had jet lag on CSU's opening drive, a nine-play, 78-yard march that included 45 yards on the ground, highlighted by Gartrell Johnson 's 4-yard rumble into the end zone.

But the Rams managed just 15 yards rushing on their four subsequent first-half drives and the Horned Frogs took a 13-7 lead into the locker room after CSU's Kory Sperry and Rashaun Greer dropped long touchdown passes from quarterback Billy Farris .

The Rams went to backup quarterback Klay Kubiak in the third quarter but they couldn't get close to the end zone in a seven second-half possessions.

They had minus-49 yards rushing in the second half and finished with just 11 yards on 28 carries.

The Horned Frogs came into the game leading the nation in run defense, allowing just 22.3 yards a game, total defense (208.8) and fewest first downs per game (10). They were also tops in time of possession (37:09) and in team rushing (246.7).

And after that first drive, they lived up to their reputation.

Aaron Brown scored on a 6-yard run and Joseph Turner punched it in from 3 yards out for TCU. The kick following Brown's TD was blocked.

One play before Brown's TD, cornerback Nick Oppenneer was hanging on quarterback Marcus Jackson 's back but couldn't bring him down and Jackson somehow completed a 5-yard pass to his tight end on fourth-and-1 from the 11.

The Frogs were 6-of-9 on third downs in the first half, including one just before Turner's TD, but Jackson inexplicably spiked the ball at midfield on third-and-1, forcing a punt in the waning seconds.

Jackson also fumbled five snaps, one of which resulted in a turnover.

It was 39 degrees at kickoff and cold, wet fans streamed toward the exits by halftime.