How many have 2 main right backs at literal extreme ends of the spectrum? 1 possibly too young and raw, the other too old
It's a conversation for another day, but when you say "too old", Coleman is 33 - yes, his best years are behind him and he's coming off a poor season, but there's an argument to be had where I could suggest his decline had been exaggerated a bit by the lack of a semi-decent team and/or cohesive tactical strategy around him over the last couple of years.
I'm not for a single moment suggesting that he's anywhere near his prime, but in the last two seasons he's had firstly James "Nah, running's not for me, chico" Rodriguez in front of him and has been badly exposed as a result or he's had this season where we've basically been an absolute disaster and you'd have been hard-pressed to shine if you were ten times the player Coleman is.
As for Patterson - let's wait and see. This view has been drawn out because of that injury he had. Impossible to venture an opinion on this just yet.
If the deal for Kenny was one year rather than three, I might think this argument made more sense, but keeping him for three years should (in theory) take him well past Coleman's retirement, and Kenny has demonstrated time and again that he's well below the standard required, so why would we be relying on him as back up for any more than one season? If it turns out Patterson isn't up to it or is a year or two away, buy a Coleman replacement next summer.