By Dan Bernstein– senior columnist

(CBS) The Cubs are still talking to teams about Starlin Castro, gauging the market for the struggling shortstop as they try to clear their middle-infield picture while tinkering around the edges of a playoff contender.

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The problem is that they’re in violation of the Branch Rickey Rule — the one that says it’s better to trade a player a year too early rather than a year too late.

Sources tell 670 The Score that what’s being proposed in exchange for Castro is underwhelming the Cubs, the market depressed by a slash line of .247/.283/.321, a flaccid .604 OPS and a .264 wOBA that ranks him 155th of the 162 qualified MLB players. That he’s not named Jorge Soler, Kyle Schwarber or Addison Russell makes him a clearance-rack item at this point, despite the fact that the three-time All-Star is still just 25.

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Castro’s fWAR is -0.4. Last year he finished at 2.7.

It’s too late.

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Dan Bernstein is a co-host of 670 The Score’s “Boers and Bernstein Show” in afternoon drive. Follow him on Twitter  @dan_bernstein and read more of his columns here.