At 27 if they were goalkeepers central defenders or even central midfielders they would be just coming to their peak. it does every now and then change, but wing backs is a young mans game and the ability to get up and down the pitch for 90 minutes a must,
as for mings he was kicked out of Southampton youth for being too small went to ipswich played left wingback to a good enough standard that Bournmouth spent a lot of money for them 12 million pounds to bring in , he then had an injury that ruled him out for a year, so last season was his first in the prem and his first as a cb, he has good football ability and pace from his lwb days and decent cb skills from playing in a poor team that did not play a 10 man defence ,
with vinny stones otta and kolorov most likely to play cb this season mings is no risk only opportunity
Zabaleta didn't do too badly between 27-30, he was one of the best right backs in the world for those few year, it was only this last 12/18 months he's really struggled. Sagna was probably 31/32 before he dropped off the cliff physically as well, so I have to disagree.
By the time Walker and Bertrand are 30/31 we'll hopefully be seeing the academy players especially from the current crop of U16/U18's coming through and taking their places.