By Nathan Ridley Manchester City have fended off fierce competition to complete the signing of midfielder Claudio Echeverri – who’s been dubbed the ‘next Lionel Messi’. Echeverri, 18, joins from Argentine champions River Plate, where former City defender Martin Demichelis is manager. Tying him down on a four-and-a-half-year contract, City are believed to have stumped up an initial transfer fee in the region of £12.5million, and agreed to pay performances-related add-ons which could take the deal up to £22m. However, Echeverri will stay at River – who the Treble winners recruited another Argent…