Mark Hughes reportedly has one game to save his job, with Saints just one point above the relegation zone after the loss to City.
But Elyounoussi believes the team can turn things around this week at home against Watford.
He said: "It's a mental thing.
"We want to forget about this game and start looking ahead to the next one to get in the right mindset.
"It shouldn't be hard to pick ourselves up after this loss and everyone has to look inside themselves and pick themselves up in time for the next game."