Borja Valero is a good player, who has been capped for Spain in more recent times, and may have been a regular for the team had he been playing 10 years back.
It sounds cliched but his problem seemed mental more than anything else. I mean, for such a good player he's been relegated twice now (one with Villareal) who are a big team in Spain. It just stinks of 'lightweight foreign player who isn't strong enough'. Of course that is Valero, and Yacob may be very different.
However, he hasn't exactly made a great 'start' if he does come.