George North's stint at Northampton Saints has been described as "like having a Ferrari in your garage but you can't find the key" by former team manager Lennie Newman.
North is to leave Northampton at the end of the season and return to Wales, having signed a National Dual Contract from the 2018-19 campaign.
Though the centre has scored 26 tries in 54 Premiership appearances, his time with the Saints has been hampered by injuries and concussions.
And Newman, whose 21-year association with Northampton ended in 2009, told BBC Radio Northampton: "It's been a bit like having a Ferrari in your garage but you can't find the key for it.
"That's not sometimes through his fault. But there are times when he's been a wasted commodity and he is a marquee player - one of the best players at the club.
"Personally, I don't think it's the end of the world [North leaving].
"You like to keep hold of your best players but to me it's just very much the king is dead, long live the king.
"We're not party to this but I wouldn't be at all surprised if he's gone for less money, less games and looking after his own interests a little bit more."