Alan Shearer could not ‘believe’ what Sunderland did in the build-up to the weekend’s FA Cup clash with Newcastle United. Sunderland endured their first Wear-Tyne derby defeat since 2011 on Saturday afternoon. The Black Cats were thrashed 3-0 on home soil – a defeat that topped off a rather horrendous week on Wearside. There had been plenty of excitement around the derby since the two sides were drawn against each other in December. However, Sunderland quickly began to frustrate fans when they allowed the Magpies to take 6,000 tickets for the FA Cup third round – meaning they would take up the…