Hagg was handled rather poorly at the AHL level. As a junior he was a competent two way defenseman with a good outlet pass. Instead of developing as that in the AHL he was instructed to dump the puck and make the "safe play" everytime. To become more physical, which coincidentally wasn't his game at all.
Unfortunately, that doesn't make you an effective NHL defenseman. He has brutal posession metrics, he plays most of the game in his own end because he can't keep the puck and his first pass ability has gone.
He is good at blocking shots, he's physical and good at closing off players behind the net. He's basically a physical Andrew Macdonald at this point in his career which is a damn shame. I had real hopes for him