Shearer has failed to win any of his four games in charge and, to make matters worse, has managed just two points out of a possible 12 with his team scoring a mere one goal.
The harsh facts are that Newcastle look doomed, even though they have moved back above Middlesbrough.
Michael Owen and Obafemi Martins squandered two glorious chances to wrap up the points as the doom descended on St James' Park and the harsh realities of relegation are began to sink in.
Shearer swung the axe to the side beaten at Spurs and out went Kevin Nolan, Ryan Taylor, Jonas Guitierrez, Andy Carroll and the injured Steven Taylor.
Shearer, knowing Newcastle needed to go for broke, went for three up front in Mark Viduka, Owen and Martins.
Fabricio Coloccini was recalled to the defence alongside the fit-again Jose Enrique, while Shearer went for just three players in the centre of the park.
Paul Hart, knowing that staving off defeat would further enhance Pompey's place in the top-flight, named three defensive holding players in midfield with Peter Crouch battling it out alone up front.
The match started with a tremendous atmosphere as United threw everything but the kitchen sink at the packed Pompey rearguard.
What they lacked in midfield creativity and guile, Newcastle made up for gritty determination but they could not create the chances their fans craved.
Momentum was lost just before the half-hour mark when Enrique pulled a hamstring following a rampaging run down the left flank and had to be replaced by Danny Guthrie.
At least Newcastle were showing a willingness that had been missing for most of the season and the fans warmed to their endeavour.
Pompey on the other hand seemed content to fight it out for a draw, though they were put to the sword in the final third of the first half.
Newcastle were furious they were not awarded a penalty with Shearer remonstrating with the fourth official after Viduka's ferocious drive clearly struck the arm of Hermann Hreidarsson.
Viduka then headed over from a Damien Duff cross before Martins got to Habib Beye's cross from the right only to blast his shot over from just six yards.
The second half was only 30 seconds old when Martins linked up well with skipper Owen before cleverly back-heeling the ball into the path of Viduka whose sliding shot was gathered by David James.
Pompey grew more as an attacking force and Hayden Mullins sent out the warning signs with a curling effort that was not too far wide.
With the likes of Alan Smith and Viduka having been out injured for lengthy spells, fitness was going to become a key element for United.
But they were almost thrown an unexpected lifeline after 61 minutes when James dropped a basic cross from Duff only for the big keeper to recover.
Then, just seconds later, Owen had the opportunity to bury the type of chance that has been his trademark over the years. The ball broke to England's forgotten man but, with just James to beat, he hit the ball straight at the keeper.
Newcastle were caught on the break after 73 minutes when Nadir Belhadj ran at Coloccini and got the better of the Argentine before forcing a save out of Harper.
Harper was called into action again when Crouch got clear, but his finish was woeful.
Pompey's continued threat from set-pieces was almost rewarded after 74 minutes when Richard Hughes came close to scoring his first Premier League goal in seven years.
However, he headed the ball against a post with Harper appearing to think it was going wide.
Newcastle needed a grandstand finish, but it never came and never looked like coming.