The Reds are embroiled in a title fight with Pep Guardiola’s side and know City must drop points for them to win the title.
Manchester United go into the match on the back of a humiliating 4-0 defeat to Everton at the weekend as well.
And Merson thinks City will win the Manchester derby ‘easily’.
He told Sky Sports: “I think the league will be won here as I expect Manchester City to win easily.
“Manchester United are just not very good. It was embarrassing against Everton and the players should be ashamed of themselves.
“They need to work hard this week, which will not be enough, but it is the least they can do. To lose the way they did against Everton was mind-blowing.
“They should be honoured to play for that club and they embarrassed it.
“There could be some nerves for City as United will park the bus.
“You need the second goal to make sure you win every game because at 1-0 you never know, there could be a set-play and then it’s level.
“I remember when Tottenham lost the league to Leicester in 2015/16 they kept chasing it against West Brom when they were 1-0 up and then West Brom get a corner, score from it, and the league is over. You need to get that second goal.
“If City win this game I can’t see how they are going to be stopped.
“They have one game a week for three weeks and, no disrespect to the teams they are playing, if they can’t win those three games with the squad they have got then they don’t deserve to win the league.”
United are currently sixth in the Premier League, three points behind Chelsea in fourth.
City are second, two points behind Liverpool but have a game in hand over their title rivals.
Guardiola knows beating rivals United will set them well on their way to becoming back-to-back champions.