Complex sentence: Modern rugby union numbering schemes normally now have the starting players numbered from 1 to 15, and the replacements numbered 16 onwards, but players have not always been identified by individual labels, nor have the systems used always been the same.
Split into simpler sentences: Modern rugby union numbering schemes normally now have the starting players numbered from 1 to 15, and the replacements numbered 16 onwards. But rugby union players have not always been identified by individual labels, nor have the systems used always been the same.