Hansen, a junior, left the Buffaloes' loss to Texas Tech in the second quarter after being hit on an option play. He was initially diagnosed with bruised ribs and did not return to play in the 27-24 loss.
Cody Hawkins, who finished the game at quarterback for Colorado, is the likely starter for the Buffaloes (3-4, 0-3 Big 12). Colorado needs three wins to become bowl-eligible and it is possible that Hansen could return for a bowl game, Colorado's sports information department said, according to area media reports.
The school said that doctors are hoping they won't have to remove Hansen's spleen. He was admitted to a Boulder-area hospital and is expected to remain there for a couple days.
"I knew he wasn't feeling well, because he's one of those kids that if he had the wind knocked out or bruised ribs, he would have been itching to get back in there and do something," said Rick Hansen, Tyler's father, according to the Longmont (Colo.) Daily Times-Call. "He just couldn't breathe."
"He's still under care," Rick Hansen added, according to the report. "[He is] just kind of resting and recuperating and trying to get better. They keep checking his blood work and they do all the precautionary things to make sure the spleen still isn't bleeding."
Hawkins, a senior, is the son of Colorado coach Dan Hawkins. He threw for 274 yards and two touchdowns in the loss, joining Joel Klatt and Kordell Stewart as the only Buffaloes quarterbacks to throw for 6,000-plus career yards.