The former manager believes the bad atmosphere at the club could be big negative.
The Magpies are currently deep in relegation trouble as they sit 19th in the table and six points from safety.
Their hopes of avoiding the drop were not helped on Saturday afternoon as they were comfortably beaten 3-1 by Southampton.
A big hope for them is that they have four home games remaining, but Souness says that could be a curse rather than a blessing given the sentiment on Tyneside.
“When you look at Newcastle, four of their six games are at home,” he told Sky Sports.
“You would say that is an advantage normally, but the way the mood is on Tyneside right that will backfire on them. Those players are playing under enormous pressure.”
While Newcastle will be concerned about the negative atmosphere, the most important issue is sorting out their awful defensive form as they seek to avoid the drop.
Newcastle's leaky defence has been something that has plagued them all season and was once again the cause of their loss to Southampton on the weekend.
It is something manager Rafa Benitez has so far failed to fix, despite that arguably being the reason he was hired, and finding someway to shore up the back-line in their remaining games will be key to their survival hopes.