Written off by most observers as a champion who had seen his day, the Sampras who stalked the courts as world number one for six straight years in the 1990s rose from the ashes to add to his lustre with a record-setting 14th Grand Slam title.
Usage notes
To have seen better days and to have seen one's day have similar meanings. However, to have seen one's day may indicate that the subject is completely worn-out and of no use whatever, while to have seen better days may indicate that the subject is not fully worn-out and still has some functionality even if it is well past its peak condition.