Are there portrayals of this in ancient art? I recall wrestling scenes on Greek vases that show ordinary-looking genitals. Except for one athlete who had some kind of string tied at the very end of his penis, nothing like what you describe.
I read speculation that the man was perhaps circumcised, which might have made him ineligible to appear in the games, which of course were held in the nude. To get around this ban, he pulled the shaft skin forward over the glans, and tied it in place (though some contend only native Greeks could compete anyway, none of whom were likely to be circumcised in the first place). This method is used today to generate a faux foreskin over time, or to lengthen an intact one, due to the ability of stretched skin to grow when held under tension for long periods.