"There is a big difference between City with Tevez and without him, " said Rosler.

BBC: Why Carlos Tevez is so important to Manchester City

The call from manager Uwe Rosler fell not to an old head, but to Marcello Trotta, a 20-year-old on-loan striker who had come on as a late substitute.

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The numbers speak for themselves, as 36 goals in 51 starts testify, but ahead of the two teams' 157th competitive meeting, ex-City striker Uwe Rosler believes Tevez offers the complete centre-forward package.

BBC: Why Carlos Tevez is so important to Manchester City

"City have to get the money back for him, " insisted Rosler, who recently suggested losing Tevez could have a "disastrous effect" on City's bid to become a major force in European football.

BBC: Strip Carlos Tevez of Manchester City armband - Rosler

"City often appear to lack enthusiasm when Tevez isn't in the side, " observed Rosler, who scored 50 goals in 153 games for City and since retiring as a player has manager Norwegian sides Lillestrom, Viking and Molde.

BBC: Why Carlos Tevez is so important to Manchester City

"Tevez is absolutely key to City's hopes, both in this match and for the rest of the season, " Rosler, who scored twice against United in the Manchester derby during a four-year spell at the club from 1994-98, told BBC Sport.

BBC: Why Carlos Tevez is so important to Manchester City

"The only thing that worries me is that he has come out in public a few times to say he misses Argentina, he misses his family, he thinks about retiring, " said Rosler, who plans to move his family back to Manchester having completed a successful two-month stint at Molde.

BBC: Why Carlos Tevez is so important to Manchester City