Against an athlete such as Hundley, defenses are generally less aggressive coming off the edges because they don't want to let the quarterback out of the pocket. When the quarterback gets into either flat, he has a better chance to find space down the field and run for a big gain. That puts the focus on how Hundley handles interior pressure from the pocket.
If Hundley corrects his ability to throw while under pressure, it should raise his draft stock more than anything else.
Footwork is vitally important for any quarterback. Some players with big arms are able to overcome their sloppy mechanics at times, but Hundley doesn't fall into that category. When he tries to throw the ball without an established base or when he is too conscious of impending contact to his upper body, his passes either become completely uncatchable or force receivers to attempt unnecessarily tough receptions.
Hundley takes a deep drop and surveys the field at the top of his drop. This gives the defense time to penetrate the pocket as one of the interior pass rushers is coming free to attack the quarterback. Because he is coming up the middle, Hundley is able to recognize his presence early and react to him before he can make contact with the quarterback.
In order to react to this pass rusher, Hundley needs to either slide to the side and quickly release the ball or stand tall and quickly release the ball before absorbing a big hit. Obviously he is exposing himself to potential injury, but sometimes that is necessary when you have to throw the ball from the pocket.
Hundley doesn't do either of these things. Instead he steps sideways with his left foot as he begins his throwing motion and his upper body wilts backwards so that he is relying solely on his arm strength to throw the ball down the field.
His intended receiver was working back to the football and needed the ball to arrive further infield than it did. Instead of throwing the ball accurately to his receiver, Hundley's pass falls short and off-target so that his receiver never had a realistic chance of catching the ball. This wasn't a difficult throw, but because Hundley couldn't handle the pressure in the pocket, he made it a difficult throw.
You never want a quarterback to be sloppy with his mechanics, but you especially can't afford your quarterback to be sloppy with his mechanics when he doesn't have a huge arm to compensate.
UCLA can minimize the impact of these missed throws from Hundley because of the design of their offense and because of the overall standard of college football. In the NFL, these kinds of plays are more problematic but also not fatal. This flaw only becomes fatal when pressures lead to turnovers that would be otherwise avoidable.
On this play, Hundley unnecessarily tries to extend the play when he doesn't have a quick throw to negate immediate pressure.
Throwing an interception while trying to make a play down the field when your offense desperately needs to score isn't a major problem, but throwing an interception when you're playing with a seven-point lead in the fourth quarter on a low-percentage pass shows a lack of understanding of situational football.
Hundley needed to understand in this situation that a sack wouldn't have been a terrible play. Ideally the offense would have converted to extend the drive, but that option simply wasn't there. You can never judge a play solely by the result, but the situation before Hundley made his decision clearly showed him that he made a bad play here.
Even if Hundley threw an accurate pass to his intended receiver, the player would still have had to spin around, beat a defender in space and run for at least nine yards before another defender could arrive to prevent the first down.
Hundley showed a severe lack of poise on this play and even though one play can't be used to judge a player's skill set, it fit with a recurring trend of poor plays against pressure from the quarterback.
Another recurring trend with Hundley came on his deep throws. The UCLA offense didn't ask him to consistently throw the ball down the field from the pocket, so again this is something the offensive design masked to a degree, but when Hundley did try to find his receivers downfield there were major warning signs about his arm strength and accuracy.
On shorter throws, Hundley's velocity is very impressive. For long stretches of games his arm strength appears to be as good as any quarterback prospect from the past two years.