Were Javi Martínez and Fernando Llorente that important to the 2011-2012 Athletic Bilbao? Yes, obviously. Bayern Munich bought Martínez in what was Bundesliga's most expensive transfer ever made. Fernando Llorente decided to move away from Bilbao next summer (his contract expires), but Marcelo Bielsa has decided not to play him much instead of trying to get the best out of him this last season.
There have been rumors around Bilbao about Athletic's players not wanting to play for Bielsa. The Argentinian coach enjoyed a very good first season, but his tactical system requires a very committed team, and it seems that Iraola, Llorente, Muniain or De Marcos don't want to run as much as they did last season.
They're still a dangerous team, though, as every football player wants to excel when playing at the Santiago Bernabéu. Winger Iker Muniain is certainly Bilbao's bigger threat without Llorente. He's very young, and he could be a very interesting fit for some European elite teams lacking some creativity and firepower upfront. Susaeta and Iraola are also very dangerous, and both of them play in Athletic's right wing, meaning that Fábio Coentrao will face an interesting challenge against them.
Bilbao has always been a very tough team to score goals against, but not with Bielsa coaching. His defensive system isn't exactly great, and they've already conceded 20 goals in just 11 games. Given Real Madrid's firepower and Benzema's likely return to the lineup, Bilbao's defender should not have an easy time trying to stop Mourinho's attackers.
It's not clear whether Llorente will stay on the bench for yet another Liga game or not. If he does sit out, former Valencia striker Aritz Aduriz will be Bilbao's striker. He's another aerial threat for Real Madrid's defenders, but he lacks the quality that Llorente has. Still, Aduriz has scored 8 goals in this Liga season, so Ramos and Pepe will need to do their best in Bilbao's set pieces.
Anyway, this 2012-2013 version of Athletic Bilbao is not better to last year's one. It seems obvious that this will also be Bielsa's last season in the club, so the Basque team will probably need to rebuild its roster. And that's not easy for them.