Manchester City have splashed out around Â£87million on Fernandinho, Jesus Navas, Alvaro Negredo and Stevan Jovetic, while new Chelsea boss Jose Mourinho has agreed deals for six new faces, including Andre Schurrle and Marco van Ginkel.
But Fletcher says the United support should not fret too much.
''We're talking about the English champions so it can't be too much of a concern,'' he said.
''We won the league last season. We should never have been knocked out of the Champions League - a bad refereeing decision cost us there.
''So if we don't sign anyone I fully believe we have the capabilities in the squad to achieve the success we want.''
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