Defense has come to play in Tallahassee, Fla., as Oklahoma takes a 13-3 lead over Florida State into the locker room at the half.

OU came out of the gate fast with a 15-play, 80-yard touchdown drive in which the Sooners ran the ball effectively against the Seminole defense.

Florida State responded with a decent drive of its own, but it ended with a 53-yard field goal by kicker Dustin Hopkins.

And after that? Defense, and lots of it.

At the half, Oklahoma has 167 yards of offense and Florida State has 115 yards.

Both teams saw their second possession end with an interception, and the Sooners were only able to tack on two field goals before the end of the second quarter.

FSU quarterback E.J. Manuel has tossed two interceptions, including one picked off by safety Javon Harris that was returned to the Florida State three-yard line, but the Sooners were unable to punch the ball in.

Some were expecting an offensive explosion in this matchup of the No. 1 and No. 5 teams in the nation, but both teams have struggled to maintain rhythm as the game has gone on.

Here are three things to watch during the second half:

OKLAHOMA'S OFFENSIVE LINE
The Sooner big men were opening up massive holes and keeping FSU's front four in check at the start of the game, but the 'Noles have seem to settle down and have brought a good amount of pressure in junior quarterback Landry Jones' face. If Oklahoma is going to stay in control, the offensive line has to keep Jones off his back and open running lanes for the Sooner backfield.

DEFENSIVE INTENSITY
After a lackluster drive for the defense, the Sooners have picked up the pressure, forcing Manuel into a string of poor decisions. However, the Sooners can't let their intensity keep them from playing assignment-smart football. Manuel hasn't looked necessarily sharp in the passing game, but Oklahoma has left some throwing lanes open for the Seminole receivers.

RED-ZONE EFFICIENCY
Oklahoma's goal-line woes last season have been well-documented, but with two drives inside the FSU five-yard line have ended with the Sooners kicking field goals. OU can't leave points on the field when playing against the No. 5 team in the nation — on the road, no less. The Sooners need to try more play-action passes when they are knocking on the door.