Relatively quiet for three quarters, South Florida star running back Marlon Mack showed up just when the Bulls needed him most.

Mack's 52-yard touchdown run on a fourth-and-1 play from the Bulls' 48-yard line late in the third quarter broke open a tight game and propelled American Athletic Conference-member South Florida to a 45-20 romp over the Atlantic Coast Conference's Syracuse Orange Saturday before 32,288 fans at the Carrier Dome.

Mack, who had 63 yards on eight carries before that touchdown, finished with 115 yards on nine carries and two touchdowns as the Bulls (3-0) outscored Syracuse 45-3 after the first quarter.

D'Ernest Johnson's 83-yard punt return for a touchdown on the first play of the fourth quarter boosted South Florida's lead to 42-20.

Syracuse quarterback Eric Dungey completed 32 of 47 pass attempts for two touchdowns and two interceptions as the Orange outgained South Florida 549-454 and held a 15-minute edge in time of possession.

Trailing 28-17 at the half, Syracuse (1-2) struck first in the third quarter on Cole Murphy's second field goal of a game, a 49-yarder with four minutes remaining. It was the Orange's first score since Murphy's 40-yard field goal with 30 seconds left in the first quarter.

Had the Orange stopped South Florida on Mack's 52-yard run, SU would have had a short field and the momentum on its side.

The Bulls erupted for four second-quarter touchdowns to erase a 17-0 first-quarter deficit. Wide receiver Rodney Adams scored three of the touchdowns on a 27-yard screen pass from quarterback Quinton Flowers, a 9-yard run and a 19-yard run.

Mack scored the other South Florida touchdown on a 2-yard run that capped a 47-yard drive. Syracuse gave the Bulls a short field after failing to convert on a fourth-and-3 play as Dungey's pass went off the fingertips of wide receiver Steve Ishmael.

The Orange, which trailed Louisville 21-0 five minutes into last week's game, scored on its first three possessions Saturday to build a 17-0 lead. Dungey capped a 16-play, 79-yard drive with a 24-yard touchdown pass to wide receiver Ervin Phillips on Syracuse's opening possession, then connected with wide receiver Brisly Estime on a 47-yard scoring strike to make it 14-0.

The Bulls improved to 3-0 for the first time since they started 4-0 in 2011. Next week, South Florida hosts a Florida State team that was rocked by Louisville 63-20 Saturday. The Orange will visit Connecticut (2-1), which tripped ACC-member Virginia 13-10 Saturday.