While I can understand why Chelsea would want Sergio*, besides the fact City would be crazy to sell him at any price, if Chelsea are looking to find strikers to lead their front line over the next few years then they are better off looking for someone like Belotti, Morata and/or PEA instead, especially the first 2.
*Although let's face it, its their own f**king fault in the first place for putting themselves in mess. What with Conte sacking Costa (which I would describe as one of the dumbest moves any manager could do), Solanke moving to Liverpool (I can see why he would want to leave, but why to Liverpool of all teams if he actually wants to progress is career? Personally I think he is better off moving to either us or Spurs) and the failure to get Lukaku (a player who actually wanted to return to Chelsea and whom the Blues in turn stupidly sold to Everton).