The 42-year-old German has had his say on the big-money switch and the potential ramifications it has for the English international - who suffered from plenty of criticism as the England squad underperformed at this summer's European Championships and were knocked out by Iceland in the last-16 of the competition.
Sterling's future in doubt after Sané arrival, says Hamann
Sterling, whose impact in an ever-improving City side weaned after Christmas, was unfortunate to suffer an injury in the latter stages of the season and consequently lost his place in Manuel Pellegrini's starting XI. As a result, he went to France shot of confidence and his performances were under further scrutiny as England lacked a cutting edge in-front of goal at the Euros.
Sané is one year Sterling's junior, and both will battle for starting berths
Leroy Sané has signed a five-year contract deal with the Citizens this week and the 20-year-old winger is an exciting acquisition to say the least.
The transfer fee is reported to be in the region of £37.5million pounds and Hamann has said Sterling is the player he'll "probably come up against" in a battle to start for Pep Guardiola's side next term.
"[Raheem] Sterling has pretty much stalled since he went to Manchester City - he's never showed the promise he showed at Liverpool earlier in his career, so I think Sterling will be the one who needs to pick it up."
Although his confidence took a blow in the later months of last season, it has been reported that Pep has spoken to Sterling and reassured him of his first-team plans involving the 21-year-old winger. With that being said, the amount of attack-minded players battling for a place in the starting XI ahead of the new campaign has increased and it'll be interesting to see how Sterling reacts - positively or negatively - to more competition for places.