The Spanish defender has made just two appearances under new Blues chief Jose Mourinho so far this season, leading to speculation that his time in West London may be coming to a close.
‘The Special One’ appears to have made Branilslav Ivanovic his right-sided defender of choice, which is likely to limit Azpilicueta’s chances of securing regular action.
This has alerted Athletic, who are keen to lure him back to his homeland.
The San Mames-based side are known for their policy of only fielding players from the Basque region of Spain, criteria that the 24-year-old fits.
Having sold Javi Martinez in a big money deal to Bayern Munich last summer, the Spaniards have the cash at their disposal to make a move for the Chelsea man.
Barcelona are also keen, but it is expected that Azpilicueta may have a greater chance of regular action with Athletic.
The full-back is believed to be happy at Chelsea, but could be tempted to make a move for regular action in the run up to the 2014 World Cup.
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