I think there are some pretty massive assumptions at play here.
There seems to be this huge misconception that Mo will just be able to click his fingers and return to his best. For me there are a couple of reasons why that is unlikely to be the case. I think there were clear signs that he wasn't as devastatingly quick as he used to be. Even before AFCON there were a number of teams who went one on one against him and managed to largely nullify him.
That never used to work because Salah's game was pretty simple, get him 1v1 and he absolutely destroyed defenders. Get him central and he would just run past people as if they were wearing lead wellies. Isolate him on the right edge of the area and he would just shift the ball onto his left foot and bend it into the far post. Everyone knew what was going to happen they just couldn't stop it.
First half of last season Salah was incredible. He had to complicate his game to achieve that though. He relied more on his skills than his out and out pace. There were far more drag backs and changes of directions. He scored a couple of absolute worldies where he stood defenders up and left them on their backsides. However, there was the nagging doubt that he was having to do more and more to score those goals.
The other thing is that we have changed the way we play. Our main attacking principle of play used to be direct and try and get Salah in space on the left side of the opposition's penalty area. With the arrival of Diaz and the form of Thiago that changed in the second half of the season. We were far more controlled in possession. Instead of relying on gegenpressing we had a couple of genuine playmakers.
Much is made of Diaz's dribbling ability. However, what impressed me more was his decision-making that was absolutely elite level. His ability to retain possession, play the right pass and still provide a threat revitiliased the way we played. We were much more content to keep the ball longer and create chances more centrally. Mane benefitted hugely from the ability of the likes of Diaz, Thiago, Keita and Trent to create chances.
With the arrival of Nunez and Carvalho I can see that process evolving even more. So even if Salah is motivated and wants to go out with a bang it may prove to be more difficult for him next season and I can see us moving away from looking to play to his strengths.