The midfielder has been crucial to Newcastle United's recent good form.
After a disastrous start to the season, which saw them sitting in the bottom three, the pressure was firmly on Steve McClaren’s side this season.
They have picked up in recent weeks though, with an impressive win over Liverpool followed by an even bigger win over Tottenham pushing them up the table.
Sissoko has been key to that, putting in big displays in those wins, and Merson has praised him for stepping up, but believes he should be doing more.
“When they went through this run you didn’t really see him, but now all of a sudden he’s come to the fore,” he told Soccer Saturday.
“He is a handful, he’s big, he’s strong and he should be taking the game by the scruff of the neck a lot more than he does.”
“But fair play to him, when they’ve needed him now he’s stepped up, and sometimes that’s very difficult when you’re not winning football matches.”
While Newcastle will be boosted by the fact Sissoko has hit form at the right time, they will be worried at the same time.
With the January transfer window looming, they will surely be fearful that he’s putting in those displays in order to catch any suitors' eye before that window opens.
That is a problem for another day though, with them now simply focused on picking up more points to get further away from the bottom three over Christmas.