Freidel was inflating a tire on a water truck, said his wife, Joni, when the tire exploded. He was struck by the exploding tire and the wheel rim.
The accident occurred on a ranch owned by friends of the Freidel family located approximately 100 miles from Casper, WY.
Freidel was taken by ambulance to the Wyoming Medical Center in Casper.
Joni said her husband suffered a head injury, a broken arm and a collapsed lung. He is in the medical center's intensive care unit after undergoing three hours of surgery.
"We have Mike and his family in our prayers," said Ed Meierkort, USD's head football coach. "Mike is a long-time friend who means a lot to me, this football program and the university," said Meierkort.
Originally of Armour, Freidel is in his third season as the assistant head coach and defensive coordinator for USD and also serves as an assistant professor in the health, physical education and recreation department.
He is in his 21st season as a collegiate coach. He has coached for five seasons at USD and 15 years at Augustana.