TALLAHASSEE, Fla. -- Mason Heintschel threw for 321 yards and connected with Desmond Reid on a pair of touchdown passes as Pittsburgh handed No. 25 Florida State its third straight conference loss on Saturday.
A true freshman, Heintschel completed 21 of 29 passes and had a pair of second-quarter interceptions in the 34-31 win. He has surpassed 300 passing yards in both of his starts, building off a rout of Boston College last week with a road upset of the Seminoles.
"He's a football player and he didn't lose any faith," Pittsburgh coach Pat Narduzzi said. "That's the difference. He fought back and didn't care [about the interceptions]."
Reid had eight catches for 155 yards and 10 carries for 38 yards for Pittsburgh (4-2, 2-1 Atlantic Coast Conference).
The Panthers closed as 11.5-point underdogs before the game, making the victory their largest upset since beating No. 2 Miami in 2017 as 12-point underdogs, according to ESPN Research.
After a promising start to the season, Florida State (3-3, 0-3) is in free fall following losses to Virginia, Miami and now Pittsburgh. Mike Norvell's team has failed to defeat an ACC opponent since a win over California more than a year ago.
FSU coach Mike Norvell was visibly upset immediately following the game and accepted the responsibility for the loss while saying his team needs to cut down on their mistakes.
"You sit there and you talk about accountability, you talk about the work, you talk about emphasis ... but we gotta do it over the course of the game," he said at his postgame news conference. "And we're just not doing that consistently enough."
Tommy Castellanos completed 16 of 23 passes for 245 yards for the Seminoles on Saturday, including a pair of touchdowns to Micahi Danzy -- 58 yards in the fourth quarter and 33 yards in the second quarter.
But after FSU went ahead 24-21 on Jake Weinberg's 34-yard field goal attempt, Florida State fumbled at midfield and then went three-and-out. Later, while trailing 34-24, came Castellanos' 58-yarder to Danzy.
"We had our opportunities," Norvell said. "We didn't do enough to overcome the negative plays."
The Panthers finished with a pair of field goals and then Ja'Kyrian Turner's 3-yard touchdown run capped an eight-play, 75-yard drive with 2:28 left.
The Associated Press contributed to this story.