There is no measurements to be made if a player isn’t fit, it’s plain to see if he went it wouldn’t be to much of a loss besides financial. In my opinion😳
WHat I don't understand is why you're saying this now, on the back of a season where he was more available than before (even despite AFCON). Same applies for Matip.
Given both their issues with availability the season before, you'd have said they were no loss (besides financial), and yet both played pretty big roles in the country's closest run at a quadruple in history. Have to look beyond 'did they have a lot of injuries' and consider their ability and contributions and whether their fitness can be better managed (as we appeared to manage last season)
Worth noting Keita was played in 23 PL games last season. Hendo had a season with 17 appearances, followed by 24 and then 27 - one of them being a sub for 1 minute (Hendo started a larger proportion obviously, but you're talking about being fit). Players get injured, yet can still return and be regularly available to contribute at a good level.