5 clubs Barcelona have angered with their transfer negotiations this summer

2) Arsenal

Barcelona were looking to bring back Arsenal's Hector Bellerin

When it comes to Arsenal, the cordial relationship went down the drain long ago. There was a time when the Gunners allowed Barcelona to use their training ground ahead of their Champions League final at Wembley. They may not be so inviting anymore.

Cesc Fabregas, Thierry Henry, Alexander Hleb, Alex Song, Thomas Vermaelen... It's an illustrious list of players Barcelona have signed from the north London club. And they don't seem to have stopped, trying their best to make Arsenal a feeder club.

Their latest transfer target was Hector Bellerin, the Gunners' promising young right-back who had made the Premier League PFA Team of the Year in 2015/16 at the age of 20.

Of course, he was a La Masia product but Wenger had ensured he would not go home empty-handed when they won over Fabregas.

Repeated attempts to lure Bellerin back to Spain have failed with Wenger informing the full-back that he was staying put no matter what.

In the end, the Gunners sent them a ‘strongly worded’ letter to warn them against chasing Bellerin's signature. Barcelona soon backed off under the threat of legal action.