But really, how many Spanish players played in serie A in the past 20 years ? 4-5 players at most.
Hardly an indication that Spanish players can't make it here.
Guillermo Amor – Fiorentina – 1998-00
Bojan Krkic – Roma, Milan – 2011-13
Borja Valero - Fiorentina - 2012-13
Arandes Toni Calvo - Parma - 2010-11
Chico - Genoa - 2010-11
José Ángel Crespo - Bologna - 2011-12
Iván de la Peña – Lazio – 1998-99, 2001–02
Roberto Delgado – Lazio – 2003-05
Alejandro Rodriguez De Miguel - Cesena - 2010-11
Dídac Vilà - Milan - 2010-11
Javier Farinós – Inter – 2000-04
Javier Garrido - Lazio - 2010-12
César Gómez – Roma – 1997-98
Josep Guardiola – Brescia, Roma – 2001-03
Iván Helguera – Roma – 1997-98
Luis Helguera – Udinese, Ancona – 2000-02, 2003–04
Óscar López – Lazio – 2004-05
José Ángel Valdés – Roma – 2011-12
Gaizka Mendieta – Lazio – 2001-02
José Mari – Milan – 1999-02
Fernando Marqués - Parma - 2010-12
Javi Moreno – Milan – 2001-02
Pedro Obiang - Sampdoria - 2010-11, 2012–13
Javier Portillo – Fiorentina – 2004-05
Martí Riverola - Bologna - 2012-13
Jaime Romero – Udinese, Bari – 2009-11
Victor Ruiz - Napoli - 2010-11
Diego Tristán – Livorno – 2007-08
Alberto Zapater – Genoa – 2009-10
That list tells you a few things; that actually Spanish players haven't done well in Serie A in the last 20 years. But that is mostly because very few were amongst the better Spanish players available at the time (Guardiola, de la Pena, Jose Mari, Mendieta being exceptions). There are a lot of stragglers there.
Also, Serie A was a stronger league than La Liga during the 90s and early 00s, so there is every chance those players would not step up to the standard. The attacking players were the biggest flops, and Spain's defences were not even close to that of Serie A in that time period.
Now La Liga is the stronger league, even if that may be amongst a small percentage at the top. Serie A doesn't have as many great defenders or great defences, but it'll be interesting to see how Llorente does. He's such an obvious target, I want to see how he handles the close attention.