Confusion surrounds the amount of Forest's initial bid for the player with one report suggesting it was less than £500,000 while others have it much closer to £1million but although Walsall chairman Jeff Bonser called the offer 'derisory', Merson felt it was fair.
"Matty is a natural goalscorer," Merson said. "He is young and he has potential, so it wouldn't surprise me if he leaves.
"Birmingham lost again, Sunderland lost again and so did Forest. It's the hardest thing in the world to put the ball in the net.
"I thought Forest's bid was quite close to his true value - especially in this day and age."