I think there was a considerable gap between Carrick and Busquets. As good as as Carrick was, he was never really an elite CM. All the bemoaning surrounding him here, for example, wasn't just because people didn't get the nuances of his role. It was also because the reference point at that time was Keane and Scholes who were clearly a cut above. Carrick was by any yard stick an excellent footballer. But he had weaknesses that held him back, he wasn't very mobile, lacked leadership, authority and dynamism (he gained two of these finally in the 12/13 RVP year) and often shat himself when pressed, and/or maybe just didn't have the quick feet to get out of those spaces. Obviously on the flip side he had a lovely passing range and screened our defence well.
Busquets was for me so much better. He was almost impossible to press in his prime. Would get out of the most uncomfortable of spaces with absolute ease. Technically he was superior - quicker feet, better close control, better short passer, better playmaker etc It's only long passing where I'd give Carrick the edge.
I think Xavi would be worse at Iniesta's role than Iniesta would at Xavi's. I do agree that Xavi was undoubtedly better and the absolute best at controlling games but Iniesta was better and unrivalled as a ball carrier and playmaking as far as attacking midfield were concerned. Two very different players who were incredible together. Find it hard to compare them as they both reached such a high level in their specific role.
As for the CL, I think overstate the whole Xavi dependency of Barca and Spain. He was an important player. However, he wasn't an important player in their last CL win. Useful but not vital. And if you have three all time greats (in Spain's case two) - Messi, Xavi and Iniesta. The magic tends to get diminished as each of them go. So just because Xavi was the oldest of the three/two, people refer to his leaving as the key moment as if that alone underpins him being the most important part.
