Starkel appeared to suffer the injury after being tackled while rolling out to his left in the third quarter, with the Aggies up 38-10. He was helped up and limped off the field with his arms around two Texas A&M staff members.
Quarterback Kellen Mond came in to replace his fellow freshman but was largely ineffective, going 3-of-17 for 27 yards passing and rushing for 54 yards on 15 carries.
Starkel was later seen on the sideline on crutches and wearing a walking boot on his left foot.
In addition to Starkel, Texas A&M defensive back Donovan Wilson also was on crutches after the game. Coach Kevin Sumlin said both players will be evaluated Monday.
Sumlin said the losses of Starkel and Wilson in the game changed things dramatically on both sides of the ball.
The Aggies led 44-10 at one point in the second half before allowing 35 unanswered points. The Bruins became the first team to overcome a 34-point deficit since Michigan State in 2006, according to ESPN Stats & Information, and pulled off the second-largest comeback in FBS history.