But Merson reckons having Ighalo will be good for Greenwood as it means the teenager will not have to be relied upon.
Greenwood, 18, has started two Premier League games so far this season but would have played a more prominent role if Ighalo did not sign.
“You feel for Mason Greenwood but at the same time I’m a bit relieved for Mason Greenwood,” Merson added.
“This lad’s going to be a good player, I think he’s going to be a proper player.
