Mathews has yet to sign his entry level contract, rumours are Lou doesn't like giving performance bonuses to rookies and considering Laine got a deal that includes up to $2.65 million in performance bonuses it's going to be interesting to see if Lou caves in and does something he hates doing.
Marner got a bonus deal from Lou last year. So it's just rumours. It's more likely Matthew's agent is being a dick as they all are to the Leafs.

