Once you have become a professional football, unless you suffer from a career ending injury, you are a professional footballer for life. It doesn't matter if you lack the required mentality, are nowhere near the required standard, have bitten fellow players, kicked fans, had affairs with team mates wives, racially abused other players, failed drugs tests etc. your career will continue as normal.
Players like Ravel Morrison have done nothing for 10 years but It genuinely doesn't matter, there always someone who will give you another chance. Many players that are not good enough will have a close call and look like their career is about to end like Hal Robson -Kanu did at the age of 26, just before the last Euros but they will always get a goal at just the right time and then their career carries on as normal.