Alan Pardew's team were outplayed by their Championship hosts, who went ahead through an expertly taken goal from Andrea Orlandi on 33 minutes and sealed victory with a Will Hoskins strike late on.
Newcastle's chances weren't helped by the sending off of Shola Ameobi, who received a second yellow card early in the second and left an already depleted side to fight on with 10 men.
Their victory was deserved and made it two years in a row that Premier League Newcastle have fallen to Brighton in the FA Cup—they were beaten 1-0 in the fourth round last season.
You might call it less of a shock this time around, bearing in mind Newcastle's spiralling form. Pardew's team have now lost seven of their last eight matches and only won twice in their last 16. They find themselves 15th in the league and just two points clear of the relegation zone.
As if defeat to Brighton wasn't hard enough to bear for Newcastle fans, it came in the same week they sold Demba Ba to Chelsea—losing their top scorer and a man who played a big part in their strong campaign last season.
These are dark days for the Toon Army, who can only hope their team has reached rock-bottom and the only way is up. The recent signing of French international Mathieu Debuchy is cause for optimism, but Newcastle will surely need to do more business in January to spark a recovery.
It says everything that many people predicted a Brighton win on Saturday.