Clifford was injured on a third-down pass play early in the second quarter. He went into Penn State's medical tent and then to the locker room for evaluation. The senior appeared on the Penn State sideline for the second half without his jersey and pads.
Clifford appeared to hold his back or rib area as he walked to the locker room.
Penn State coach James Franklin had no update on the nature of Clifford's injury or the status of other players injured in the Iowa loss, including starting defensive tackle PJ Mustipher, reserve safety Jonathan Sutherland and reserve running back John Lovett. Franklin did take issue with Iowa fans booing Penn State defensive players who were injured.
"They don't run a tempo offense," Franklin said of Iowa. "This wasn't part of our plan. I don't think that's the right thing for college football."
Sophomore Ta'Quan Roberson replaced Clifford at quarterback and struggled, throwing for 36 yards with two interceptions.
Despite accounting for two interceptions himself, Clifford helped Penn State to a 17-3 lead before exiting, passing for 146 yards and rushing for a team-high 33 yards and a touchdown. A third-year starter from Cincinnati, Clifford entered the game with 1,336 pass yards and 11 touchdowns with three interceptions, on 67.3% completions this season.
Clifford started his 26th career game Saturday.