That list is far beyond anyone's comprehension. I'll never make a list again.
Evans and Jones and Mertesacker and Koscielny and Rojo above Cahill. - This will take a while:
Cahill is made to look good by Mourinho's defensive organization. He is a very limited player, excellent at heading and last ditch tackles but has many weaknesses such as his propensity to back away from runners.
Koscielny was one part of the best CB partnership in the league. His absence has been sorely missed.
Rojo was a rock during Argentina's final run.
I've browsed through United forums for years and have so often seen Evans being referred to as United's best CB, even while Vidic and Ferdinand were still around (albeit in the midst of their decline)
Jones- Fergie wouldn't talk so highly of him for nothing, he is versatile, and his first appearances for United in 11/12 showed his potency as an attacking threat. Not for nothing was he compared to Beckenbauer, even if that was a little hyperbolic
Balotelli. - Has been poor with Liverpool I admit but his mercurial talent is undeniable. Has come up big at a major tournament before (Euro 2012)
Sczeszny. - A few dodgy moments but overall an extremely good keeper who has saved Arsenal many times. Also broke into the team at a young age which is a testament to his quality
Hart. - Was the best keeper in the league back in 11/12. Was poor the following season and a bit but class is permanent and all that and he's been vert solid since then. You don't hold a place down at an elite team without being quality
Blind. - Key part of the Holland team that finished 3rd in the World Cup, also those gourgeous assists on the big occasion
Badstuber. - Guardiola rates him so highly, Bayern fans often say he would be the best defender they have if not for injuries.
Piqué.- A starter as Barca and Spain won everything. Recent form may be poor but I'd say class is permanent
Maicon - Was once the best RB in the world, fell off after that but has since regained much of his form at Roma
Menez. - Milan fans often call him their best attacking player. May be a tad generous, wanted to give some love to one of the world's biggest clubs
Lavezzi.- Played so much for the excellent Napoli and now PSG sides, starter in Argentina's World Cup Final run and played well in that match
Explanations in bold.