According to this story in The Guardian, Liverpool contacted Manchester City to find out exactly what amount they were looking for in exchange for Carlos Tevez. When the offer of a swap of Carroll for Tevez was discussed, City's Football Administration Officer Brian Marwood immediately shot the deal down.
Carroll has only scored 6 goals in 35 appearances since making the move to Anfield last January. The £35 million transfer from Newcastle made Carroll the eight-most expensive footballer in the world. His lifestyle and training habits have been criticized since the move, most notably by England manager Fabio Capello.
Tevez has seen possible transfers to AC Milan and Paris Saint-Germain fall through in the last month. Since his massive falling out with manager Roberto Mancini, Tevez has been persona non grata at City.
Neither player is expected to play any serious amount of football in the next six months.