Manchester City have been told that splashing out £100million for Jack Grealish was the perfect tonic to spark his teammate Raheem Sterling back into top form.
Cast aside by Pep Guardiola either side of his Euro 2020 heroics, England forward Sterling looks to have once again cemented his place in the Premier League champions' starting XI.
Heading into the Tottenham game, Sterling had notched 13 goals and five assists this season.
That is considerably more than summer signing Grealish - who was ruled out of the Tottenham game due to a shin problem that caused him issues at Aston Villa.
City missed the chance to move nine points clear at the Premier League summit after their defeat to Spurs.
Speaking about Sterling to Sky Sports, Souness said: " I don't believe the game has changed in this respect. If you're a big player, you want to be in playing every game.
"What motivates you more than anything else is someone coming in that might take your place in the team.
"Those guys [City] know that if they have two or three indifferent games, they could be on the bench watching."
Souness added: "When you've got that many match-winners in your team... and City have so many special players.
"They've got so many threats going forward. If you were playing against them you'd think 'okay, I'll stop [Bernardo] Silva, I'll try and stop [Kevin] De Bruyne' and then they hurt you from somewhere else and that makes them a great team.
"Dropping two points from November, it's absolutely phenomenal."
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