K.J. Costello passed for an SEC record 623 yards and five touchdowns in the Mississippi State debut of coach Mike Leach’s “Air Raid” offense, and the Bulldogs knocked off sixth-ranked and defending national champion LSU 44-34 on Saturday.

Costello’s passing yardage in his first game since transferring from Stanford to Starkville, Mississippi, eclipsed the 544 yards Georgia’s Eric Zeier had against Southern Mississippi in 1993 to set the Southeastern Conference record.

And Costello needed most of it to make up for his two interceptions and two lost fumbles, which helped LSU rally to tie the game at 34 before he engineered a pair of scoring drives in the final 10 minutes.

LSU became the first defending national champion to lose its opening game since Michigan in 1998 lost at Notre Dame.

LSU quarterback Myles Brennan intermittently showed promise in his debut as starter in place of 2019 Heisman Trophy winner and 2020 top NFL draft choice Joe Burrow. But Brennan’s 345 yards and three touchdowns passing could not make up for the trouble the Tigers’ inexperienced defense had in new coordinator Bo Pelini’s scheme.

Four of Costello’s touchdown passes covered between 24 and 75 yards. The longest came on Kylin Hill’s catch and run in which the running back slipped safety Todd Harris’ tackle along the sideline to break into the clear. Osirus Mitchell caught touchdown passes of 43 and 24 yards, the second putting the Bulldogs back up by two scores with 3:39 left. Tyrell Shavers caught a 31-yard touchdown pass and Austin Williams had a 9-yard TD catch.

LSU transfer linebacker Jabril Cox, who played at FCS power North Dakota State, scored LSU’s opening touchdown on an interception and 14-yard return.

Terrace Marshall Jr. had touchdown catches of 37 and 33 yards, while freshman tight end Arik Gilbert leaped in front of a defender to turn Brennan’s desperate throw as he was going down into a 2-yard score.

But Brennan often struggled to make quick and decisive reads. He was sacked seven times and the first of his two interceptions came when linebacker Jordan Davis hit the QB’s elbow as he threw. The ball went straight to cornerback Esaias Furdge at the Bulldogs 24.

MISSING DEFENDERS

LSU played without two of three returning starters on defense, including one of the top players in the nation. All-America cornerback Derek Stingley, who also returns punts, was hospitalized overnight Friday after unexpectedly falling “acutely ill,” LSU said. LSU spokesman Michael Bonnette emphasized that the illness was not COVID-19 and added that Stingley was expected to rejoin the team after being evaluated by physicians. Senior defensive tackle Glen Logan also was scratched from the lineup unexpectedly. Sophomore Cordale Flott and freshman Eli Ricks started at cornerback for LSU. Flott was beaten on MSU’s first TD and Ricks on the second. Freshman Joseph Evans started for Logan.

THE TAKEAWAY

Mississippi State: The Bulldogs could not have asked for a much better start to the Leach era. If teams around the SEC weren’t taking the “Air Raid” seriously before, they are now.

LSU: The Tigers’ loss of prominent personnel in the offseason — including 14 players taken in the NFL draft — and lack of experience on the field was exposed during pivotal moments of a tense opener. In terms of talent, LSU appears to have plenty of upside, but time will tell how long it takes to be realized.

POLL IMPLICATIONS

LSU is bound to plummet after giving up so many yards and points at home. Mississippi State, meanwhile, has made its case to crack the AP Top 25.

UP NEXT

Mississippi State: Hosts Arkansas on Saturday.

LSU: Visits Vanderbilt on Saturday