Wijnaldum joined Newcastle during the summer transfer window, and he has gone on to make an immediate impression - scoring six times in the Premier League already.
Four of these goals came against Norwich City, and Merson believes that if the Dutch midfielder keeps putting in performances of that quality, then he will soon attract attention from clubs around the world.
"When he came over I thought he was outstanding, but he went off the boil," Merson said. "But he is a good player, he showed that against Norwich.
"You don't want him to be one of those players [whose form depends on] what side of the bed he gets out of. That's what he was turning into. If he performs like he did against Norwich, he could be playing for one of the big, big boys.
"I mean no disrespect by that, because Newcastle's a big club, but teams will go and watch him."
Many of Newcastle's recruits over the summer have failed to make a positive impression, but Wijnaldum is one of the additions which appear to have been smart business.
The Holland international has added power and strength to their midfield ranks, while he also has the ability to score all kinds of goals.
Wijnaldum has scored from headers, close-range finishes and from distance, meaning that he looks to be the complete midfielder.
Despite Wijnaldum's good form, Newcastle still haven't been able to make a strong start to the season and they currently sit in 19th place in the Premier League table, two points adrift of safety.