It shouldn't hurt their legacy.On th3e contrary it should help the legacy by taking on a challenge when you are shot and maybe even being competitive. For example Holyfield ''losing'' to Valuev helped his legacy not hurt it.
Ray Robinson is one of the greatest of all time and his record is 175-19-6. However he was 128-1-2 by his 31st birthday, and that is why he is the considered best.