Missing a whole year in 2013 killed off a lot of crucial development that would have happened that year. In 2012, Golson was asked to simply protect the ball, and not lose the game.
It's one thing to play the game in minimum risk mode. It's another thing to take command of the field, and make the higher risk throws with confidence.
In 2014, after a year of inactivity, Golson was asked to take command. Had he played in 2013, transitioning from a conservative role to a commanding one, I truly believe he would have been one of Brian Kelly's best quarterbacks. Alas, he lost his mojo in the 2nd half of the season when the going got tough, and he didn't know how to pull himself together.
If Matt LeFleur were working with Golson without that year of inactivity, I think he could have helped guide him through those tougher times. It's much easier to put the finishing touches on a polished mind.
Since he was only here for a single year, it's difficult to say whether or not he would have been a great QB coach here, but the way Malik Zaire played in the Music City Bowl, along with that good game against Texas in 2015, along with how Deshone Kizer turned out when being forced to play in the 2nd game of 2015, makes me believe that LeFleur had some positive impact on the guys.