SYRACUSE, N.Y. (AP) - Backup quarterback Trevor Siemian hit Demetrius Fields for a 9-yard touchdown pass with 44 seconds left and Northwestern held on to beat Syracuse 42-41 Saturday in the teams' season opener.

Siemian, subbing for starter Kain Colter, drove the Wildcats 75 yards in 10 plays, taking advantage of a critical personal foul against Syracuse defender Keon Lyn for a late hit out of bounds on the previous play.

The decisive score in the sweltering Carrier Dome came after Ryan Nassib had engineered a stunning comeback for the Orange, throwing for four second-half touchdowns. Nassib finished 44 of 65 for 470 yards. His completions obliterated the school record of 29 he'd shared with Marvin Graves and Andrew Robinson.

Nassib threw a pretty 20-yard TD to Christopher Clark in the left corner of the end zone with 2:40 left in the game for the go-ahead score, and Prince-Tyson Gulley ran in the two-point conversion to give the Orange a 41-35 lead after they had trailed 35-13 in the third quarter.

Nassib also hit Marcus Sales for a 7-yard touchdown and combined with Jeremiah Kobena on scores of 50 and 7 yards, the latter with 6:42 left in the fourth to move Syracuse within 35-33.

Syracuse was still in it at halftime despite the heroics of Northwestern star Venric Mark, who scored twice and accumulated 203 all-purpose yards in the first half.

Mark, who rushed for 82 yards, returned three kickoffs for 49 yards, giving him a school-record 1,514. Ricky Edwards held the previous mark of 1,499, set from 1979-83.

Colter was 14 of 21 for 135 yards passing and ran for another 40 yards on 14 carries.

The loss continued a downward spiral for the Orange, who posted a 5-2 mark to start last season, then lost their last five games to miss a chance to play in a bowl game for the second straight year.

Syracuse was undone by big plays much like last season, when the Orange allowed 16 touchdowns on runs of at least 20 yards and passes of at least 25 yards. Even with a beefed-up defense, they were unable to stop Mark in the first half, and it cost them dearly.

Mark returned a punt 82 yards for a score in the final minute of the first quarter, racing untouched the entire way as he weaved across the field. His 53-yard punt return set up a 14-yard TD pass from Colter to Christian Jones late in the second, giving Northwestern a 21-13 halftime lead.

In between, Mark caught a scoring pass from Colter, easily beating the defender in the left corner of the end zone. That play was set up by a Syracuse turnover. Northwestern linebacker Chi Chi Ariguzo intercepted a deflected pass and returned it 44 yards to the Orange 21. Sales had tried to make the catch of Nassib's low throw and it caromed up to Ariguzo's waiting hands.

Syracuse was victimized on a short screen pass behind the line of scrimmage on the third play of the third quarter, and it proved critical. Nassib's throw to Jerome Smith in the left flat was low and behind him and bounced harmlessly away as players on both sides pulled up, thinking the play was over. Ariguzo then picked up the ball, looked around and ran 33 yards into the end zone in a stunning turn.

Mark's 32-yard run set up Colter's 1-yard touchdown run, giving the Wildcats what appeared to be a commanding 35-13 lead midway through the third.

After Sales scored for the Orange, Nassib hit Kobena for a 50-yard touchdown, an easy play after defender Quinn Evans fell down.

Syracuse, spurred by the Carrier Dome crowd's deafening cheers, forced a punt and scored again. Gulley's 21-yard run set up Nassib's 7-yard scoring pass to Kobena with 6:42 left. Nassib's pass for the two-point conversion failed and the Wildcats still had a 35-33 lead.

Syracuse gained a 6-0 first-quarter lead on field goals of 22 and 33 yards by Ross Krautman and Gulley's 14-yard run up the middle on second down gave Syracuse a brief 13-7 lead early in the second.

Syracuse was expected to try to get the ball to 6-foot-4, 229-pound freshman Ashton Broyld, a triple threat like Colter but with no college experience. After sitting out the first half, Broyld received his indoctrination but was used sparingly in the sweltering heat as the temperature outside hovered near 90.