In the 2012 and 2013 seasons, O'Brien guided the Nittany Lions to a 15-9 record despite sanctions, highlighted by a signature four-overtime White Out victory against Michigan, before he left for the NFL.
Allen's goals entering pro day were to showcase his speed and hands to representatives from all 32 NFL teams.
A large crowd of students flocked to get one last glimpse of No. 26 before he heads off to the NFL in late April.
"For me to say, 'Oh, I had a good run, it's time for me to move on,' I felt like I was being a hypocrite, because that wasn't the mindset that got me here."
Christian Campbell, DaeSean Hamilton, and Saeed Blacknall were a few of the top performers from Penn State's annual pro day.
"Saquon Barkley is a franchise-type talent that promises to be one of the first players selected in the upcoming 2018 NFL Draft. We’re thrilled to partner with him in such a meaningful way as he begins his NFL career."