According to Colombian journalist Diego Rueda, Arsenal are showing interest in FC Porto attacking midfielder Juan Quintero:
Es real la posibilidad de que Juan Fernando Quintero juegue con el Arsenal. Estaría llegando el lunes a Londres. Ojalá se concrete.— Diego Rueda (@diegonoticia) July 31, 2014
According to the ol' translate button, that reads "The possibility of Juan Fernando Quintero to play with Arsenal is real. On Monday it would be coming to London. I wish becomes a reality." The reality here, though, is contingent on a number of things, and there are reasons to be skeptical. Quintero has a hefty buyout clause, and FC Porto generally don't sell on the cheap:
Arsenal already have a wealth of attacking midfielders, including the man Quintero would presumably replace, Santi Cazorla (around whom rumors float as well). 40 million euros is an awful lot even for a 21-year old, and although Quintero had a good season at Porto last year, and a decent world cup, this is the kind of move that seems unlikely given that Arsenal, so far, have only spent realllly big on proven world-class players. If Porto came down on the price a fair amount, it would seem likely, but for now, don't get your Quintero-shaped hopes up.
UPDATE: it appears that reports are saying the move is meant to be for 20 million euros: