It is the responsibility of each teammate to make sure they do their part to contribute and not become a consistent burden. If a teammate isn’t pulling their weight, then the team will have to work harder than they should. This is no problem over a short period of time if someone has an extenuating circumstance. If that exception becomes the rule, the ordinary team gets acclimatized to carrying the lagging teammate. Over time this will be a morale killer as teammates carry more than they signed up for and watch others skate by with no accountability.