Actually there performance has already reduce do to the injury of Mohammed Salah because if Mohammed Salah had been on that match there is every chances that Liverpool would have won the match because there last meeting was not easy on Fulham because Mohammed Salah put a big pressure on them but watching there match yesterday the pressure was not that strong, although I'm not saying that Liverpool will no longer perform well but on the contrary what I'm saying is that the performance of Liverpool will no longer be the same again since Mohammed Salah is not there, however is going to affect there position on all the leagues they are because other team will take advantage and push them down from there current position on the table.
Mohamed Salah, Liverpool's main player, has made quite a big contribution to the team, so if he is absent, of course it will have a small impact on the team's performance, but this doesn't have too big an impact, so I think whether Salah is present or not, the Liverpool team will still be strong.
I think what happens in the domestic league will be different from the Europa League because each team has a different focus in each competition they participate in.
I would guess that the impact will be a major one, but it also depends on who they are playing against. Looking at who they have/had games against, they weren't games that Liverpool needed Salah for, and they did alright so far without him.
I think he is a major player when it comes to bigger teams, because when you are playing against a great team, you will need every good player you have, and he is their best player, so when playing against a good team, they will need Salah. It's just AFCON, it will be over soon, and until the end of the season, they will do their best .Lucky for them that City missed KDB nearly all season so far, and Haaland is missing now, so while Liverpool is missing players, so does City, which makes them equals.