Sunderland continued their impressive start to the Premier League campaign since promotion from the Championship by beating Newcastle United 1-0 at the Stadium of Light on Sunday afternoon.
Nick Woltemade netted a bizarre own goal just a minute into the second half to secure the win for the Black Cats who jumped up to seventh.
Speaking on The Rest Is Football podcast, Shearer tore his former side apart in what was a dire performance.
"I wasn't (okay). Newcastle were dreadful.
"They were rotten and I was really shocked at how dreadful they were because, I mean, that is pathetic in any game, let alone in a derby game.
"Seriously, you're going to play in the biggest game of the season at your rivals, and you've heard all the players all week, 'We know how much it means to the fans and we're going to do this and that.' Well, lads, they did nothing. They were awful, honestly."
Newcastle have now not won any of their last 10 games against Sunderland in the Premier League, and their European hopes are now in tatters as they sit in 12th place in the table.
The return Premier League fixture at St James’ Park is scheduled for 21st March 2026 as Howe’s side seek revenge near the end of the season.