Three Lions supporters clamoured for Grealish to start against Croatia on Sunday but Southgate opted for Raheem Sterling instead and the Manchester City man notched the winning goal.
Many are expecting England to make changes for the Scotland clash tonight with Grealish still waiting on his first minutes at the tournament.
However, Merson – who played 101 times for Villa and played and managed Walsall from 2003-2006 – believes Southgate will avoid playing the Villa skipper to ease pressure on himself to pick him again.
“Southgate has to be careful with his selection against Scotland as he does not want to bring unwanted pressure on himself by making too many changes,” said Merson via his Sky Sports column.
“If he brings in Jack Grealish and he rips it up, people are going to want him to play every game. But he will not play against Scotland. If you play Phil Foden, Grealish, and Mason Mount all in the same team, then when will England be getting the ball back?
“Sterling played well, Foden showed glimpses, Harry Kane struggled as he kept on coming short into a packed midfield, where he was never going to find space, he needed to go the other way and stay up top if he wants to get involved with the team.
“We just need to get him chances, but even if he does not score in his first four games of the tournament, he will still play in the fifth.
“But he has to change it up against Scotland, 100 per cent. He might swap a Foden for a Jadon Sancho, or Marcus Rashford.
“The problem with playing Grealish, though, is the whole nation wants him to start as he is the ‘new Gazza’. He is a top-drawer player, don’t get me wrong, but I do not think he fits into Gareth’s plans. And if he plays him and he rips it up, then Gareth is under severe pressure again when he does not need to be under that pressure.
“And that is why I do not think he came on against Croatia, as it was made for him with Croatia chasing the game 1-0 down. No-one keeps the ball better than Grealish.”
Many pundits have predicted Foden could be rested in place of Grealish, meaning England will keep the attacking threat of Sterling’s runs in behind the defence.
There are concerns, however, over Grealish’s fitness as he trained away from the rest of the squad on Tuesday and did individual work in the gym.
He missed a large chunk of Villa’s season with a shin injury and only made his comeback in the final weeks of the Premier League season.
Despite that, the 25-year-old is ‘desperate’ to play.
“Not even just in this tournament, I’ve made a name for myself (in other big games) during my career. I’m desperate to be involved,” he said via TalkSPORT.
“But the main thing is the team get the three points and carry on our good start.”