Chasing a club record tenth consecutive win, the Magpies struggled to find their mojo in front of a capacity crowd, the visitors belying their lowly position in the table with a resolute display.

Ironically, what was to prove the winning goal followed what was arguably United's brightest spell of the game, Matt Ritchie and Jonjo Shelvey both coming close to breaking the deadlock midway through the second half.

However, it was at the other end of the pitch where the afternoon's pivotal moment came, as former Celtic defender Mulgrew volleyed home after a short corner.

Ahead of Tuesday's EFL Cup quarter-final at Hull City, boss Rafa Benitez made six changes to the side who saw off Leeds United six days ago, and - in the first half in particular - Newcastle found clear cut chances hard to come by.

Indeed, it was Blackburn who started the brighter, Owen Coyle's side coming within a whisker of an opener early on.

Five minutes in, Liam Feeney's well-weighted cross from the right was met by Danny Graham, who saw a looping header tipped over the crossbar by Karl Darlow.

It took almost a quarter-of-an-hour for United to register a first meaningful attempt at goal. Ritchie profited from a hurried clearance to play through Aleksandar Mitrovic, and the Serbian's left-footed strike deflected just wide of the near post.

Just shy of the hour-mark, Mitrovic set DeAndre Yedlin away down the right, and the American's driven cross bobbled up invitingly for Christian Atsu, but the winger was crowded out inside Rovers' six-yard area.

The Magpies continued to improve as the first half wore on, and Yedlin himself saw a first-time strike fly wide from 20 yards after Blackburn failed to clear their lines from Ritchie's set-piece.

United began the brighter after the break, and - with 48 minutes on the clock - Atsu sliced narrowly wide of the near post after running onto Ayoze Perez's dinked cross.

Isaac Hayden then saw a piledriver from distance flash wide, before Ritchie narrowly cleared the crossbar after substitute Paul Dummett's delivery was missed by Mitrovic.

The visitors continued to pose a threat themselves, however, and, on 65 minutes, Marvin Emnes just failed to keep a left-footed effort on target after gathering fellow frontman Graham's flick-on.

The Magpies then came agonisingly close to an opener twice in quick succession. Shelvey was the first to threaten, forcing Blackburn 'keeper Jason Steele into a fine save from distance after catching the ball beautifully in a central position.

The stand-in skipper stepped up to deliver the resultant corner, which dropped for Mitrovic just inside the area. The Serbian's mis-hit effort landed at the feet of Ciaran Clark, who failed to connect properly six yards out.

But, with a quarter-of-an-hour remaining, United were hit by a sucker punch.

Feeney gathered Craig Conway's corner from the left, and the ex-Bournemouth winger picked out Mulgrew with an in-swinging cross, who stylishly found the net from 12 yards.

As Newcastle pushed for a leveller, Emnes twice came close to doubling Blackburn's advantage.

First, he saw a left-footed strike blocked by the backtracking Hayden, before skewing just wide of the near post with time to pick his spot.

The hosts' best chance of a leveller came and went just seconds into six minutes of injury time.

Dwight Gayle - introduced with five minutes remaining - looked set to find the net after meeting Ritchie's cross 12 yards out, but the in-form forward failed to keep his effort on target, 'keeper Steele grateful to see the ball fly harmlessly high of the woodwork.

Newcastle United: Karl Darlow, DeAndre Yedlin, Ciaran Clark, Chancel Mbemba (Dwight Gayle 85), Jesus Gamez (Paul Dummett 55), Jonjo Shelvey, Isaac Hayden, Matt Ritchie, Ayoze Perez, Christian Atsu, Aleksandar Mitrovic.

Substitutes: Matz Sels, Jamaal Lascelles, Vurnon Anita, Mohamed Diame, Yoan Gouffran.

Blackburn Rovers: Jason Steele, Derrick Williams, Jason Lowe, Charlie Mulgrew, Darragh Lenihan, Craig Conway, Corry Evans, Liam Feeney, Ben Marshall, Sam Gallagher (Marvin Emnes 62), Danny Graham.

Substitutes: David Raya, Anthony Stokes, Hope Akpan, Ryan Nyambe, Wes Brown, Elliott Bennett.

Referee: David Coote

Bookings: Newcastle United - Isaac Hayden (83); Blackburn Rovers - Craig Conway (24), Jason Lowe (68).