Hackenberg announced his intention after the Nittany Lions' 24-17 loss Saturday in the TaxSlayer Bowl against Georgia, a game in which he left early with a shoulder injury.
Hackenberg suffered a sprained right shoulder during the second quarter and did not return, but he said it is not believed to be serious. ESPN draft analysts Mel Kiper Jr. and Todd McShay both have listed the 6-foot-4, 228-pound Hackenberg as fifth-best among draft-eligible quarterbacks and third among underclassmen.
"It was tough," Hackenberg said. "You've invested so much into a place and invested so much into fixing things and making sure it's where it needs to be."
The No. 1 quarterback nationally in the 2013 recruiting class, Hackenberg signed with Penn State despite the sanctions handed down to the school in July 2012. He helped keep together much of the Nittany Lions' recruiting class that season, and he went on to have a promising freshman year under the tutelage of former coach Bill O'Brien. As the Big Ten Freshman of the Year, Hackenberg threw for 2,955 yards and 20 touchdowns.
"I don't know if you can count on one hand how many other programs would have been able to survive what we survived," Hackenberg said. "Just to be a part of that is really humbling. I'm proud to be a part of that group of guys."
Hackenberg's production dipped over his final two seasons after James Franklin was hired to replace the outgoing O'Brien before the 2014 season. He threw more interceptions than touchdowns as a sophomore and averaged fewer than 200 yards passing per game for the first time in his career as a junior. Over his final two seasons, Hackenberg was sacked 82 times, most in the country.
In three seasons, Hackenberg passed for 8,457 yards, 48 touchdowns and 30 interceptions. He started every game while at Penn State, compiling a 21-17 record.