It is speculation, but a reasonable one. He was probably about as good as Van Persie overall, and the only player we have who is actually consistently aware of the runners around him. Cleverley and Anderson are not good for this at all. When those two were paired together during 11/12, they were playing in a team whereby every single player was at the absolute height of their game. It was absolutely freakish, and they've been paired together since with nothing like the same success. Nevertheless, during that period our midfield was cut open a lot due to not having a player like Carrick to maintain structure. Again, this is a far more important job than having someone running around making tackles.
I'm not sure which seasons you're comparing there, but if you mean we conceded more last season than 11/12 (I don't if this is true - I'm just assuming this is what you mean), then the start of the season must be taken into account here, with Carrick playing in defence, and with our entire defence playing like a load of maniacs. It was only when Carrick was paired with Cleverley that the team became less of a mess.
One further thing to consider...just how many players could pair with an aging Scholes and keep shape in midfield? It's an amazing effort by Carrick to make that work - look at Juventus and Italy by comparison who have gone with a midfield 3 in recent times to accommodate Pirlo.
I edited this in; Hargreaves and Anderson did the job at times, but it lacked composure and guile for periods of games (though our team was so good that year that it didn't really matter). It's good in theory to have a player that presses but it needs to be done in view of balance. This is why Carrick was first choice and ended up pairing with Scholes when it mattered; it's more important to have a player that is able to keep defensive shape whilst also having ability on the ball, because you get a greater defensive benefit with a player who offers a more rounded contribution.
You're right - England don't have such a player, but if they did, say, have that Owen Hargreaves, it'd make for an inferior midfield in comparison to what could potentially be fielded. Carrick/Wilshere/Rooney is pretty much perfect in theory, so chucking someone like Hargreaves in for Carrick would make it less complete in terms of what it offers.
This is why tonight's substitution was so mental. Carrick is a fantastic defensively minded midfielder - one of the best. You absolutely do not substitute a player like that when you're a goal up! It is incredible that someone capable of making that sort of decision is managing any international football team.
Anyway, I'm probably making more of a point than is necessary to argue here, but I remember last time we had this discussion I was banging my head against the wall trying to put across the importance of someone like Carrick, and how someone like that is pretty much integral for a team wanting to have a midfield that ticks every box.
Ideally, you'd want one of the other midfielders to be the complete package, but midfielders like that are few and far between, and you are more often left with a player offering significantly more of one side of the game than the other. It's unwise in that situation to sacrifice more important attributes like creativity and ball retention in favour of 'ball winning', which is what you would run the risk of doing by fitting a Hargreaves type into the England or United midfields. Further, putting a ball winner in Carrick's position and expecting him to be rigorous in tracking runners and narrowing angles is a big ask and, again, requires a pretty amazing player. Even more so if the team don't really press as a unit.*All this being said, this is not to try and be overly rigid. An unbalanced team on paper can look more balanced than any other team if the players gel correctly, but the teams discussed here - England and United - have looked distinctly 'ungelled' in recent times. That 11/12 one at the start of the season worked for example, like I say, because every single player looked like they were born to play with one another. Tactical failings on paper are less significant if player performance compensates for that.
