The Toon's all-time top-scorer has stepped in to try and save his hometown team from an unimaginable drop into the Championship, with United currently third-from-bottom in the Premier League standings, two points shy of safety.
But while all and sundry on Tyneside continue to rejoice at the return of their local hero, managers of the Magpies' rivals near the foot of the table have been less than overjoyed at the news.
“Alan will add 10 or 20 percent to their performances," said Ricky Sbragia, boss of Newcastle's fierce local rivals Sunderland, who sit in 14th place, three points above the danger-zone.
"It’s bad news for everybody in trouble at the moment. The Newcastle players will be happy and he’s appointed a very good No.2 in Iain Dowie.”
While Gareth Southgate, whose Middlesbrough side lie beneath Newcastle in 19th, is also fearful of the 'Shearer effect'.
“His arrival will change the emotions of the crowd at Newcastle," he said. "The critical factor may be 52,000 fans and the change in their beliefs.”
Shearer has just eight games to save the club he joined for a then world record transfer fee of £15 million from demotion to the Championship.
And his Bolton counterpart Gary Megson believes the likeable Geordie's appointment will give the club a huge lift.
“It’s a good move for Newcastle and it makes it a lot harder for everyone else," he said. "Newcastle were at a point where they had to do something different.”
Shearer’s first game in charge is against Chelsea at St. James’s Park on Saturday.
NEWCASTLE FANS! Check FourFourTwo.com’s ever-expandinginterviews archivefor more stuff to read:
Web Exclusives Les Ferdinand
Q&A Joey Barton
One on One Michael Owen, Kevin Keegan, Les Ferdinand, Faustino Asprilla
Boy's A Bit Special Steven Taylor, Danny Guthrie
Ask A Silly Question John Barnes
Perfect XI Ruud Gullit
What Happened Next? Tony Cunningham
My Secret Vice Nolberto Solano, Sam Allardyce
Plus! Rate Newcastle players (and others) on Talentspotter
