TEMPE, Ariz. (AP) -- After a disheartening loss to LSU, Arizona State's practices weren't exactly hearty. With Sam Keller running the offense, the Sun Devils were in a different mood by the next kickoff.

Keller passed for four touchdowns and freshman Keegan Herring ran for 197 yards and scored twice, leading No. 18 Arizona State to a 52-21 win over Northwestern on Saturday night.

``It's nice to know we can have a very average week of practice and still come out and turn it on in a game,'' said Keller, who was 20-of-31 for 409 yards and has thrown for 1,448 yards and 15 TDs in his four career starts.

``I've never had a quarterback learn what we're doing this fast,'' coach Dirk Koetter said about Keller, who didn't start a game until he replaced injured Andrew Walter under center before the Sun Devils' win over Purdue in the Sun Bowl.

The Sun Devils (2-1) rebounded from the 35-31 loss to third-ranked LSU last by accumulating a school-record 773 yards, 532 in the first half. Rudy Carpenter, Keller's backup, ran 2 yards with 2:30 left to push the total past the 743 yards the Arizona State had against Stanford in 1981. The output also was a Northwestern record for opponent yardage, eclipsing the 713 gained by Iowa in 1983.

The game took on aspects of an NFL exhibition in the fourth quarter. Neither Keller, Herring nor Wildcats quarterback Brett Basanez played the final 15 minutes, which began with Arizona State leading 45-14.

Basanez passed to Shaun Herbert for 7- and 5-yard TDs. Herbert had a career game for catches (8) and TDs. In the fourth quarter, C.J. Bacher threw 12 yards to Rasheed Ward for a final score by the Wildcats (2-1).

Carpenter also directed a TD drive, finishing with a 7-yard pass to Brent Miller with 6:57 left in the game.

Keller, who threw for 461 yards against LSU, tossed a 36-yard scoring pass to Jamaal Lewis, a 24-yarder to Derek Hagan, went 15 yards to Rudy Burgess and 30 yards to Matt Miller.

Herring scored on runs of 2 and 5 yards, but sent a groan through the home crowd by fumbling at the end of a 67-yard run with 6:00 left in the first quarter. Reggie McPherson recovered for the Wildcats, but Herring, who fumbled twice in the game, scored on Arizona State's next possession.

``Usually, if you fumble two or three times in a game, especially for a freshman, you get sit down real quick, so I just thank my coach and my O-line for having faith in me,'' Herring said.

``We knew all week, game plan-wise, that we were going to get Keegan in there and force the ball to him,'' Koetter said. ``We thought if we could do that successfully our play-action game would come, and it did. We made some big plays off play-action.''

The Sun Devils put the game away by scoring on six straight possessions in a 13:52 span of the first half and taking a 38-14 lead on Burgess' catch and run with 3:00 left in the period.

``It got away from us in the second quarter, and I'm disappointed in the fact we didn't play better,'' Wildcats coach Randy Walker said.

Each drive had a big play -- a 39-yard hookup from Keller to Burgess before Herring's tying TD; a 16-yard catch by Hagan before Lewis' scoring reception; Keller's 65-yard pass to Matt Miller to set up a 27-yard field goal by Jesse Ainsworth that made it 17-7; a 14-yard pass to Lewis before Hagan's 24-yard scoring grab; and 38-yard completions to Moey Mutz which preceded Herring's 5-yard TD run and Burgess' scoring grab.

``They were making a lot of great passes, and the running game, but like last week I just don't think guys were in their gaps, including myself,'' middle linebacker Tim McGarigle said. The Wildcats allowed 37 points to Northern Illinois in their previous game.

Early on, Northwestern's Marquis Cole had a 57-yard punt return, but the Wildcats stopped their momentum with an offensive face-mask penalty, and Joel Howells missed a 43-yard field goal.

Basanez marched them 80 yards in 1:58 on their next possession, setting up the game's first score with a 34-yard play -- a 27-yard pass to Ross Lane, followed by a roughing-the-pass penalty on linebacker Dale Robinson that moved the ball to the 7.

Banasez passed to Shaun Herbert for the TD with 7:23 left in the quarter.

But it was all Arizona State after that.

The Sun Devils slowed the pace in the third quarter, using Herring, who ran for 134 yards and one score in a 63-16 rout of Temple on Sept. 1, to grind out first downs and burn up the clock.