His fears were quickly allayed.
Kenny Hill threw for 283 yards and four touchdowns in less than three quarters as No. 9 Texas A&M rolled to a 73-3 win over Lamar in front of the largest crowd for a college game in Texas history.
It was the first game in the newly renovated and expanded Kyle Field and drew a record crowd of 104,728.
After delay of 2 hours, 5 minutes, Texas A&M (2-0) wasted no time getting going. Hill found Speedy Noil for a 44-yard pass on his first throw and Trey Williams had a 33-yard touchdown run two plays later to make it 7-0.
"It was a weird set of circumstances to start the game," Sumlin said. "For young guys I was worried about how they would handle it, but they were excited to play. I think the crowd had a big part in that when we came back out. I was shocked that everybody was still there and it was a great atmosphere to start the game."
Hill threw touchdown passes of 24, 51, 18 and nine yards in his second game since taking over for 2012 Heisman Trophy winner Johnny Manziel. He threw for a school-record 511 yards in an upset at then-No. 9 South Carolina last week.
"The more reps you get the more comfortable you are going to be in the offense," Hill said. "I think that's how it is for everybody. The more reps I get, the more time I get to get out there with the wide receivers and get a better connection with them."
Caleb Berry was 16 of 42 for 153 yards and an interception for Lamar (1-1) which was facing a Southeastern Conference team for the first time since 1974
"Obviously we were outmatched tonight," Lamar coach Ray Woodard said. "I liked the way we fought and came out and played tonight. It will be good to get back on the bus and head back to Beaumont."
Hill was replaced by freshman Kyle Allen with about five minutes left in the first half and the Aggies up 31-3, but returned to start the third quarter.
He sat down for good with 1:56 left in the third and A&M up 45-3.
The Aggies led 14-3 when they fumbled a punt return. It didn't matter much as Deshazor Everett intercepted the first pass of Lamar's next drive. The Aggies cashed in on the error when Hill hit Sabian Holmes on a short pass and he tip-toed down the sideline for a 51-yard score late in the first quarter.
Hill completed three straight passes on his final drive of the first half with the last one coming on a 9-yard touchdown strike to Edward Pope to push the lead to 31-3.
He picked up where he left off when he returned for the start of the third, capping the first drive of the second half with an 18-yard touchdown pass to Malcome Kennedy that made it 38-3. Hill completed 17 of 26 passes.
"I think these guys understand that we've got to get better and we're going to approach it that way this week," Sumlin said. "
Freshman Myles Garrett starred on defense for the Aggies, finishing with five tackles, two sacks and two QB hurries. The Lamar offensive line couldn't do much to slow down the 6-foot-5, 255-pound Garrett, who was rated as the top high school defensive end in the nation last season.
"It's a learning experience for him," Sumlin said. "He can create his own pass rush and that's something that we need."
The lopsided game gave Texas A&M fans a first look at Allen, who Hill beat out in camp for the job. Allen was considered the best quarterback prospect in the nation coming out of high school. Allen was 12 of 16 for 122 yards with an interception and he threw touchdown passes of two and 33 yards in the fourth quarter.
Noil had 71 yards receiving, a punt return for 67 yards and a kickoff return for 53 yards to finish with 191 all-purpose yards for A&M.
Lamar's only points came when the Cardinals had a first down at the 1-yard line but couldn't push it in and settled for a 20-yard field goal that made it 7-3 in the first quarter.