He can't redshirt. Pursuant to NCAA regulations, in a redshirt year, an athlete may attend classes, practice with the team, and dress for play but the athlete may not compete during a game.
Common belief notwithstanding, NCAA redshirt rules state that any amount of participation in a competition (even one play in a football game) will trigger the use of a season of eligibility, and therefore that athlete may not redshirt that year.
A "medical hardship waiver" (NCAA bylaw 14.2.4) may be granted an athlete who appears in fewer than 30% of the team's games (with none coming after the midway point of the season), then suffers a season-ending injury.
It is important to note that Iowa doesn't make the decision. A formal application has to be submitted to the NCAA through the Big Ten office requesting the waiver together with supporting medical records, MRIs, x-rays, etc. If the decision is denied by the Big Ten office, the denial may be appealed to the NCAA. As a result, the decision is entirely out of Iowa's hands.