Karl Darlow's debut disaster plunged Newcastle into further relegation trouble as West Brom triumphed at The Hawthorns.
The goalkeeper allowed Darren Fletcher's header to squeeze past him on his Barclays Premier League debut to hand Albion a 1-0 win.
Darlow was only a late replacement for Rob Elliot after he was taken ill in the build up to the game and dropped to the bench.
Fabricio Coloccini cleared off the line from James Morrison while he and Paul Dummett hit the woodwork for the Magpies and Victor Anichebe struck the bar for the Baggies.
Defeat left the Magpies in the bottom three and two points from safety while Albion's first win in six games moved them six points above the drop zone.
Saido Berahino started on the bench for the eighth straight game with Anichebe given his first Premier League start since May.
Boss Tony Pulis insisted pre-match Berahino was lucky to be a substitute and hinted at internal problems.
Darlow's tone was set when he had to be rescued inside two minutes of his top flight bow by Coloccini when the skipper hacked Morrison's shot off the line.
The former Nottingham Forest custodian then turned Morrison's drive wide before Albion survived a scare.
Moussa Sissoko had stolen the ball inside Newcastle's half and his lung-bursting 60-yard run was only halted by a last-gasp challenge from Gareth McAuley as the midfielder prepared to pull the trigger.
Both sides were prepared to press during an entertaining opening and Aleksandar Mitrovic saw a shot deflect over while Dummett blocked Fletcher's drive.
Darlow looked nervy, skewing a punch over his own bar, and Albion noticeably targeted the keeper at set-pieces.
But they could not force a first-half opener and almost fell behind 10 minutes after the break.
Newcastle had started well and Dummett's header hit the underside of the bar and Coloccini's follow up was deflected onto the post.
Chris Brunt was then forced to clear Mitrovic's effort over his own bar - as the striker called for a penalty - with the Baggies ragged.
Newcastle's plight forced them to up the tempo and s ensing the danger Pulis called for Berahino, with the striker replacing Morrison with 20 minutes left.
But it was Anichebe, who had faded after a bullish first half, who came closest on 74 minutes.
Darlow's nerves got to him again and he shanked his clearance behind for a corner and from the resulting delivery Anichebe's header bounced onto the bar.
But Darlow did not escape a second time when his error gifted Albion the lead 12 minutes from time.
Claudio Yacob's cross was met by the unmarked Fletcher and Darlow should have dealt with his downward header but allowed it to squirm past him and over the line.
The keeper made a smart save from Anichebe to prevent Albion doubling their lead and then turned Berahino's drive wide with four minutes left but his gaffe proved costly.