The Blaugrana side may be forced to come up with a 'Plan B' to reinforce the right flank of their defense due to this setback.

Just when things seemed to be going in the right direction for Barcelona regarding some potential moves, a new obstacle has emerged for Los Culés.

The team had already agreed terms to see Chelsea's captain César Azpilicueta on a free transfer next summer, but they forgot to check the player's contract in full to be sure about their options.

Azpilicueta had even agreed personal terms with the club since he is out of a contract next summer, but the main problem has been brought to light in a recent report by EFE.

The player is entitled to negotiate terms with any team he wishes from January 1 until the end of the season, but the player forgot about an optional clause included in his deal that could see Chelsea extending his contract regardless of the player's desires. This deal would keep Azpilicueta at Stamford Bridge for the next two seasons if the club executes that clause.

Now, it seems that the player will have to negotiate with the club not to execute the aforementioned clause, since that would deter his plans to join Los Blaugranas this summer. Right now, the club is focused on winning the FIFA Club World Cup title, and both parties will be forced to sit down and talk about this issue once they return to England.

If Barcelona fail to add Azpilicueta to their roster, the Blaugrana club has reportedly named Ajax defender Noussair Mazraoui as their first alternative. Nevertheless, the Moroccan footballer will only sign with the Spanish side if negotiations between Chelsea and Azpilicueta fall apart.