Both clubs will be looking to get a win at St James’ Park in order to avoid relegation.
“The game at Anfield was never going to seal our fate, but the Middlesbrough match is a massive one, not just for us but for them as well,” Shearer said in the Daily Telegraph.
“It will go a long way to deciding the outcome of the relegation fight for both of us.
“There’s no question that it is the biggest game of my Newcastle career.
“It’s the biggest game in the Newcastle career of anyone who is connected to the club at the moment.”