Souness says Arsenal are currently the best team outside the top three, as the table shows.
But he has warned they must improve away from home to fight off competition from the likes of United and West Ham.
"Right now they're the best of the rest," Souness said on Sky Sports.
"The front three for me are considerably better than any of the other teams.
"But I'm sat between Man United, Arsenal, Spurs, maybe West Ham will think they'd be in that argument as well.
"Fourth is within their reach but we're only halfway through the season.
"They have to improve on their away form, that's not good enough.
"We've seen when they went to Liverpool a couple of weeks ago that the level that Liverpool play at and where [Arsenal] are right now is considerably different.
"Yeah they have a chance of being fourth but Spurs will be in that argument, Man U will be in that argument, and West Ham I think can cause problems to anyone they play."
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