If Mohamed Salah's injury is serious, it wouldn't be good for Liverpool. Losing their best players in a mid-season African Cup will end their leadership joy. Hamstring injuries can be serious.
The moment Liverpool make a mistake, Manchester City take the lead and never let it go. From then on, the balance in the Premier League will not change easily. City had given other teams enough advances. Liverpool and Arsenal couldn't use this well. They needed to collect more points. City with De Bruyne won't lose points easily anymore.
Bad news for the Reds because they had to lose a key player due to injury while defending their country at the AFCON event and I think this will be a major blow that is difficult to overcome. Jurgen Kloop will certainly not be calm when he hears this news and he must immediately rotate his players in the next match in order to still win. Without Mohammed Salah, Liverpool does not have a dangerous attack and usually his agility and speed can make it easier for Liverpool to break into the opponent's goal.
Manchester City are certainly very happy to hear this news and hope that Mohammed Salah will be absent for quite a long time. They can more easily take advantage of Liverpool's current situation and at any time can displace Liverpool at the top of the standings. De Bruyne's return is an improvement in performance for Manchester City and the absence of Mohammed Salah will be a disaster for Liverpool.