Where to even begin...
Michael Carrick was one of the Premier League's best players last season and imo was United's best player. Our midfield situation is complicated and any new player would have to satisfy a number of criteria before making the transfer worthwhile.
Doesn't hold a candle to Yaya though, shouldn't we be aiming to match up to our main rivals in terms of quality, seeing as it was Yaya overrunning our midfield (including Carrick) that ultimately cost us?
—Can he play with Carrick in a two man midfield?
We play 442 and so finding the right partnership in the center of the field is crucial to our success in all other areas. Scholes is ideal as Carrick's partner, but he's old so he can't play every game. Anderson and Cleverly can each play well alongside Carrick, as well as looking good when played together as a pairing.
They may 'look good' but they are a defensive shambles, I think that's pretty widely recognized by now. I'd be fecking trembling at the thought of them two playing in a two man midfield, which then means we still need Carrick alongside them.
—So is he better than Anderson or Cleverly?
This is a difficult question to answer since it's very difficult to gauge exactly how good those two are at the moment. Each look potentially world class on their day, but alas each have been very unlucky with injuries; if they can stay injury free for a season then who knows how much progress they'd be able to make? It's entirely possible that not many players exist who'd get into a team ahead of Ando and Cleverly in twelve months time. Of course, we also have Nick Powell who'd like one play next to Carrick also.
I don't think either have ever looked like world class players. Cleverley is the more likely of the two to turn into a really good player at this stage, but he is never going to be anything close to a Keane or Scholes either. Yeah I know, naming two of the best midfielders in the last 20 years, but this is Man Utd isn't it? We've bought some of the best players of the last 10-20 years in other positions (Rio, Vidic, Rooney, Ronaldo, maybe Nani), why can't we do that in midfield too?
—Is he better than Carrick then?
Perhaps the new midfielder could replace Carrick rather than play alongside him? But this is a tough ask for any player considering how good Carrick's last season was and how indispensable he's shown himself as being over the years; we're at a stage in which we're about as reliant on Carrick as we are on Rooney imo, so any new player would have to be pretty fecking good to be able to get his name on the teamsheet ahead of the former.
Carrick is 31. How long can he rely on him? Yeah, he had a great last season, but what about the two years before that? Can we really rely on him to be our sole defensively minded midfielder, because we don't have anyone else in the team who can do what he does. Besides, it's not Anderson and Cleverley we should be limiting game time to (if they're fit) if we buy another midfielder, it's Scholes and Giggs. I mean, they're really old, it's not like the can get any better. If anything Giggs showed last season that he's probably done, and Scholes had 6 months off, which he won't have this season. Can he do it for another year? He couldn't before, that's why he retired.
—Will he be used as an understudy to Carrick then?
Is he happy to be sat on the bench? If this new midfielder isn't already better than Michael Carrick then he's not gonna be getting many games ahead of him; he'll have stiff competition from both Anderson and Phil Jones (who I wouldn't rule out as becoming a quality midfielder just yet) for the role of backup DM, we're not exactly struggling for depth but rather immediate quality and experience. Is there room for another midfield understudy at the club?
Again, I see no reason why he should be sitting on the bench. I mentioned above about Scholes and Giggs. There's also the fact that Carrick seems to be our first choice in defense whenever everyone else there inevitably gets injured. I also very much disagree on Jones, he would be a total disaster in Carrick's position, likewise Anderson is about as defensively adept as a rubber duck.
Basically I don't think there's much room at United for any player in CM who isn't already significantly better than Michael Carrick, and replacing Carrick with somebody better just isn't a priority since he's the complete opposite of a weak link in the squad. The main reason for certain fans crying out for a new CM seems to always boil down to the injuries suffered by Ando and Cleverly, if it weren't for those injuries we'd be sorted with Carrick, Scholes, Anderson, Cleverly, Powell and Phil Jones to choose between for two roles in the team, and as far as I'm aware neither Anderson nor Cleverly have any long-term issues that suggest they're gonna miss much football over the coming seasons.
But what happens if Carrick gets injured? Look at our policy right now, we have been buying players in plenty of areas we are well stocked in. Jones, Young, Smalling, Kagawa, potentially RVP. Have those players suffered a shortage of games? No, they've had plenty. Clubs inevitably get injuries, Carrick doesn't have a particularly great injury record at all, we also play 55-60 games a season. Will Carrick play all of them? Because we sure as hell don't have anyone who can do what he does. I don't see how his position, a position in the most important area of the pitch that only he can currently play, should not be equipped with at LEAST a backup player, or ideally a really talented youngster in the mould of Jones who can take over from him whilst still playing a good amount of games this season.
In short, I just think SAF is happy with this area of the squad. I'm sure he'd love to have carte blanche to go out and sign any player in world football to improve our midfield, but since he doesn't (nobody does) and since not many players would actually improve us all that much anyway as long as Ando and Cleverly can push on, I just think he's preferring instead to focus his attention and the club's cash on those areas he's always without much ado done well in, i.e. world class Wingers and Strikers.
It wouldn't take an awful lot to improve that midfield. Not to be overly blunt here, but it's just not very good. I think Anderson and Cleverley are talented without either having the potential to become the next big thing.
I very much agree with the bolded part though, I've said for quite a while that SAF would rather ignore the midfield and persist with the proven, albeit old players he has whilst he still can, and focus on areas he has always had a good record of signing players in instead.
Sorry for multi-quoting, but your post was rather long!