Fitzgerald underwent an MRI following the game, but definitive results weren't expected until Monday morning, according to the sources.
A source told ESPN NFL Insider Adam Schefter that Fitzgerald suffered a bruised lung.
According to sources, Fitzgerald, who made two catches on Arizona's game-winning drive in overtime, was originally checked for a concussion after he "took a hard shot." The medical staff realized the injury was in the chest area, but the Pro Bowl wideout refused to leave the game, the sources said.
Fitzgerald's father, Larry Fitzgerald Sr., originally tweeted his son's injury Sunday night.
Fitzgerald Sr. wrote: "Cardinals Pro Bowler Larry Fitzgerald suffered a Lung injury was spitting up blood on sidelines. Will have MRI MONDAY."
While the younger Fitzgerald declined to disclose his own ailment after the game, he did reveal that quarterback John Skelton fainted in the team's locker room before the game.
"Pre-game he scared us all. He fell out and he had a little fainting issue in the locker room," Fitzgerald said. "We were all nervous about him being ab le to play today and he fought through that and was able to go out there and perform and get our team a win. That shows the kind of toughness he has."
Chris Mortensen is a senior NFL analyst for ESPN. Information from ESPN NFL Insider Adam Schefter and The Associated Press contributed to this report.