In reply to Bottom Clinger:
Perhaps this German report had some effect
However, the probability of being substituted on and off increases in response to an infection, which leads to a shorter time on the field (on average). At the intensive margin, we are able to identify a significant deterioration in infected players’ productivity as defined by the literature (e.g. passes) by about five percent after an infection. This effect becomes visible right after a player’s return on the pitch but remains persistent for far more than six months. This is different to, for example, influenza-related infections
https://www.dice.hhu.de/fileadmin/redaktion/Fakultaeten/Wirtschaftswissensc...