After then-pending medical clearance prevented him from participating in the NFL Scouting Combine last month, the former UCLA star linebacker has since received clearance and NFL scouts will be looking for the versatile defender to go through a full battery of drills.
NFL Media analyst Lance Zierlein believes scouting buzz of a potential top-three pick could follow.
"What I think is going to happen, because I've seen some of his workouts from over a month ago, I think he's going to kill it," Zierlein said. "I think everyone's going to be talking about whether he's a top-three pick. I think he's going to be the most buzzed-about prospect after his pro day, that's my prediction. There will be discussions about whether he should be the first pick of the draft."
One NFL scout already thinks he merits the top pick. Jack was first cleared for running in January, and has been rehabilitating his knee injury full-time since withdrawing from school last fall. He was injured in practice days after the Bruins' third game of the season, and announced his intention to enter the draft as an underclassman and withdrawal from school days later.
"I'm not really concerned about the times. I just want to see how he's moving around and how he's recovering from his injury," said NFL Media analyst Daniel Jeremiah. "He's already way up there (on draft boards). This is just one of these deals where he can solidify his spot."
Four of five analysts who have published mock drafts project Jack to be chosen No. 5 overall by the Jacksonville Jaguars. There isn't much room to climb any higher in the draft, but for a prospect coming off a season-ending injury who hasn't worked out yet, anticipation is nevertheless plenty high.
"I think you want to make sure he looks the part with his movements, and I mean all of it -- how he bends, flexibility, lateral movement -- you want to make sure he looks exactly the way he looked on tape before his injury," Zierlein said. "I think you want to see his explosion numbers match up with what you see off the tape."
Jack said at the combine that some clubs have discussed with him the possibility of playing safety at the pro level. Whether he plays linebacker or safety, his pro-day performance could ensure that he won't last long.