Former Celtic man Mulgrew stroked home from the edge of the box to earn the hosts all three points from a game in which they mustered just three shots on goal at Ewood Park.
But Newcastle, who were dominant throughout, were left to rue their failure to capitalise on the chances they created as Owen Coyle’s side earned their second 1-0 win over United in the Sky Bet Championship this season.
After a scrappy opening ten minutes, United – backed by almost 7,000 supporters behind the goal at the Darwen End – had the first sight of goal. Isaac Hayden won the ball in the middle and exchanged passes with Mo Diame, but the England Under-21 international’s shot from 25 yards flew wide of the target.
Rovers broke away down the right shortly afterwards, with Liam Feeney delivering a high, looping cross which evaded former Sunderland frontman Danny Graham in the middle but fell kindly for Craig Conway. The Scot, though, took too long to get the ball out of his feet, and the opportunity to pull the trigger was lost.
Just before the 20-minute mark, with the contest yet to truly spark into life, Diame almost provided a moment of magic. A superb turn took him past his man, and after striding forward, his rasping 30-yard drive cannoned back off the crossbar, with goalkeeper Jason Steele stranded.
Rafa Benitez’s men were enjoying plenty of the ball, and leading scorer Dwight Gayle was next to try his luck. Paul Dummett, playing his 100th game for the club, lofted a pass into his path on the right-hand side of the box, and after cutting inside, Gayle saw his low, left-footed effort tipped away by Steele.
A beautifully disguised through ball from Yoan Gouffran gave the former Crystal Palace forward another chance to opening the scoring ten minutes before the break, but ex-Middlesbrough stopper Steele again denied him, this time rushing out to block.
And in the half’s dying moments Gayle turned provider as his cross found Gouffran at the far post, but the Frenchman didn’t make a clean connection with his volley and Steele comfortably repelled it.
Five minutes into the second period, Gouffran went close again, this time curling a shot just past the upright in front of the travelling Newcastle supporters. United then had the ball in the back of the net three minutes later when Matt Ritchie’s inswinging free kick was nodded on by Gouffran and Gayle headed home, but he was adjudged to be offside.
And just before the hour, they had the ball in the net again as Ciaran Clark found the target at the second attempt after Gayle’s free kick had been deflected into his path. This time, referee Andy Woolmer ruled it out for handball.
With the Magpies now piling on the pressure, Hayden latched on to a Diame flick and crossed from the byline, but Clark’s volley was tipped over at full stretch by Steele.
Some hesitation at the back allowed Blackburn to register their first shot of the afternoon with just 22 minutes remaining, but substitute Sam Gallagher couldn’t keep it on target as he fired it wide.
And on 73 minutes – against the run of play – the hosts took the lead. Marvin Emnes was brought down on the edge of the box and defender Mulgrew, who scored the winner in the reverse fixture at St. James’ Park back in November, blasted low past Karl Darlow, putting Owen Coyle’s side ahead with what was their first shot on target.
The goal prompted the introduction of Ayoze Perez as Newcastle looked the get back on level terms in a game which they had dominated, but Rovers held firm. A corner from the left led to another Hayden shot, but he couldn’t find a way through a crowded penalty box.
And, despite Christian Atsu and Daryl Murphy both being summoned from the bench, United were unable to find the leveller their pressure deserved in the closing minutes.
