Johnny Manziel CLEVELAND, OH – DECEMBER 13: Quarterback Johnny Manziel #2 of the Cleveland Browns warms up prior to the game against the San Francisco 49ers during the first half at FirstEnergy Stadium on December 13, 2015 in Cleveland, Ohio. (Photo by Jason Miller/Getty Images)

Johnny Manziel — a first-round pick in 2014 — hasn’t played in the NFL since 2015 after well-documented off-the-field struggles caused the Cleveland Browns to release him.

In February, Manziel revealed that he was diagnosed with bipolar disorder and depression “about a year ago” and had stopped drinking. He claims to be making a serious effort to get his life back on track, and will play football in the Spring League in April.

And while it’s likely a longshot, Manziel still hopes to make an NFL comeback.

That makes Thursday a very important day for the former Texas A&M star, as Fox Sports’ Bruce Feldman reports that Manziel is expected to throw to receivers at the University of San Diego’s pro day. It’s assumed to be the first time Manziel has thrown in front of NFL organizations since 2015.

Now, organizations are mainly there to watch the San Diego prospects , but you can be sure they will all be keeping a close eye on Manziel.

And putting aside Manziel’s off-the-field struggles, many evaluators were skeptical of his game translating to the NFL level. Much of his success at Texas A&M was a result of schoolyard-style plays that are much more difficult to make work in the NFL, and there were doubts about his ability to be a good pocket passer. Additionally, he has a small frame for the position, measuring in at 6’0″, 207 pounds at the 2014 NFL Combine.

Manziel indeed went on to struggle in his two seasons with the Browns, throwing seven touchdowns, seven interceptions, and putting together a 74.4 passer rating over 14 games. Maybe some of it is was typical struggles from a young quarterback, maybe some of it was a bad supporting cast, and maybe some of it was everything else he was dealing with carrying over to the football field. But his quarterback play did nothing to prove the skeptics wrong.

So, even if NFL organizations believe in Manziel the person now, they may simply not believe in Manziel the quarterback.

Then again, with how desperate organizations are to find quarterbacks, perhaps one will be willing to give him a shot in training camp. But Manziel likely needs an impressive showing on Thursday and in the Spring League to get that chance.

About Matt Clapp

Matt is an editor at The Comeback. He attended Colorado State University, wishes he was Saved by the Bell's Zack Morris, and idolizes Larry David. And loves pizza and dogs because obviously.

He can be followed on Twitter at @Matt2Clapp (also @TheBlogfines for Cubs/MLB tweets and @DaBearNecess for Bears/NFL tweets), and can be reached by email at mclapp@thecomeback.com.