Ohio State quarterback Braxton Miller drops back to pass against...

Ohio State quarterback Braxton Miller drops back to pass against Illinois during the first quarter of an NCAA college football game in Columbus, Ohio. (Sept. 7, 2013) Credit: AP

COLUMBUS, Ohio -- Kenny Guiton took over when Braxton Miller left with a sprained left knee, running for one touchdown and passing for two on Saturday while leading No. 3 Ohio State to a 42-7 victory over San Diego State.

Miller watched the last three quarters from the sideline after being sandwiched between two tacklers on the Buckeyes' seventh offensive play. The Buckeyes (2-0) didn't need him.

Guiton, who helped save Ohio State's 12-0 season a year ago, had the most playing time he's ever had in a game. He set career bests with 19 of 28 passing for 152 yards and 83 rushing yards.

It was another disappointing outing for the Aztecs (0-2), who lost 40-19 to FCS Eastern Illinois at home in their opener.

Guiton came in having completed 14 of 25 passes for 144 yards and two touchdowns with two interceptions in his 16 career games. He had totaled 59 yards rushing on 14 attempts.

Ohio State dominated from the outset, but a crowd of 104,984 at Ohio Stadium sat in stunned silence when Miller was injured on Ohio State's first offensive series.

On fourth and 1 at the Aztecs 12, Miller carried to the right side and then cut back. He was trying to squirm for an extra yard or two when he was hit by defensive back King Holder while going backwards, with middle linebacker Jake Fely then hitting him and knocking his helmet off.

Miller lay on the turf for a short time, rubbing his head. He was attended by a doctor, and eventually left the field under his own power, although he limped slightly. A team physician on the bench manipulated his left knee and he grimaced in pain.

Miller was taken from the field on a cart.

In came Guiton, who on the very next play handed to freshman Dontre Wilson, who sprinted around end for a 7-yard score.

The senior from Texas also tossed a 27-yard scoring pass to Corey Brown and then handed off to Jordan Hall for a 4-yard score with 3 seconds left in the first quarter. During the lull before the ensuing kickoff, Miller received a loud ovation as he jogged across the field from the ramp leading to the locker room to the Ohio State sideline.

Miller, wearing a large knee brace, remained on the sideline the rest of the game, never putting on a helmet but occasionally speaking to coach Urban Meyer and his teammates.

Meanwhile, Guiton was large and in charge.

Just like they did a week ago in rolling to a 23-0 lead, the Buckeyes got off to a big early lead. This time, however, they didn't allow the opponent to get back in the game as Buffalo did in Ohio State's 40-20 victory.

Guiton kept around the left side on a 44-yard scoring run. Rod Smith, coming off a one-game suspension for an unspecified violation of team rules, tacked on a 1-yard touchdown to make it 35-0 at the half.

It wasn't the first time in which Guiton came on in relief of Miller and grabbed the spotlight.

Guiton had taken over for an injured Miller late in last season's eighth game, against Purdue. Trailing by eight points with 47 seconds left at his own 35-yard line he led the Buckeyes to an improbable touchdown and then threw a 2-point conversion pass to force overtime. The Buckeyes won 29-22 on the way to the sixth unbeaten, untied season at the school.

Guiton hit a leaping Brown on a 24-yard scoring pass in the third quarter.

His only mistake was a second-quarter interception by cornerback Damontae Kazee -- leaping, twisting, one-handed grab that will probably end up on a few highlight reels.

San Diego State, which went 9-4 a year ago and played in a bowl game for the third season in a row, didn't get on the board until late in the third quarter. Backup quarterback Quinn Kaehler flipped a 2-yard scoring pass to Chad Young to make it 42-7. Kaehler, who completed 22 of 36 passes for 216 yards and a touchdown with one interception, took over for starter Adam Dingwell after he was intercepted by Doran Grant on the Aztecs' second possession. Dingwell finished 0 for 5 passing with the pick.

Just a year removed from finishing 20th in the nation with 221 yards rushing per game, the Aztecs were limited to 64 yards on 27 attempts. Last year's leading rusher, Adam Muema, coming off an ankle injury in the opener, carried just three times for five yards.

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