This all seems to be a bit of a clusterfuck with reports suggesting Sevilla want rid ASAP to free up a non-EU slot to bring in another player, but we're not keen on taking him back unless we're shunting him straight out somewhere else.
So he's still training in Seville, but won't feature in any games.
Complicaciones de última hora para la salida de Barco - Vamos Mi Sevilla
Valentín Barco, ha sido otro de los fichajes fallidos de la dirección deportiva de Víctor ... Leer maswww.vamosmisevillafc.com
I know that's mentioned at the end of article you posted but AFAIK Sevilla only have two non-EU players (Marcao and Barco) so they can buy and register Juninho (Brazilian striker from Qarabag they are targetting) even with Barco still in squad. So I think real reason they want to offload Barco is to free up his wages.