Farfan (centre) and Gavranovic scored Schalke's key goalsTwo goals from Jefferson Farfan and one from Mario Gavranovic saw Schalke come from behind to beat Valencia and reach the last eight of the Champions League.Valencia took just 17 minutes to cancel out Schalke's first-leg away goal as Ricardo Costa produced a smart header.But Farfan levelled just before half-time with a superb free-kick.Gavronovic then put Schalke ahead with a scrambled effort which hit both posts and went in before Farfan sealed things in injury-time with a clever chip.Schalke came into the game in disappointing form and with question marks over the long-term future of...