We've seen a few of them. Not just star players. Not just all-rounders or seriously good players in one aspect. They virtually carry the whole team. Whom can you consider as one-man teams?
One example, for India, would be Kapil Dev in the 1980s. When the Indians lost a lot of their top batsmen, before Azhar and Tendulkar, he was virtually their top batsman. Ian Botham was not too far from this role, though he had a stronger team. At times, Imran Khan would do it for Pakistan, notably in the 1992 World Cup, before Inzamam and Wasim Akram came to the fore. Then there was Chris Cairns- first the strike bowler, then the superbat for NZ. England's most recent example would be Flintoff, when fully fit. A longer-serving example for New Zelanad these days would be Vettori. Among specialists, I can think of Brian Lara and Muralitharan, at present.