TOON 0 BLACKBURN ROVERS 1
26. Karl Darlow
22. DeAndre Yedlin
18. Chancel Mbemba 85'
2. Ciaran Clark
27. Jesus Gamez 55'
11. Matt Ritchie
14. Isaac Hayden
12. Jonjo Shelvey
30. Christian Atsu
17. Ayoze Perez
45. Aleksandar Mitrovic
3. Paul Dummett 55'
6. Jamaal Lascelles
8. Vurnon Anita
9. Dwight Gayle 85'
15. Mohamed Diame
20. Yoan Gouffran
28. Matz Sels
Newcastle's nine-game winning run came crashing to an end as Charlie Mulgrew's second-half strike secured Blackburn a deserved 1-0 victory at St James' Park.
Rafael Benitez's side would have created history if they had made it 10 wins in a row in all competitions for the first time in Newcastle's existence, but instead the hosts saw their lead at the top of the Championship table cut to two points.
Jason Steele made second-half saves to deny Jonjo Shelvey and Ciaran Clark, but Blackburn matched their opponents throughout and claimed a second away win of the season when Mulgrew volleyed home from a corner with 15 minutes left.
Benitez's decision to make six changes from the side that won at Leeds last weekend suggested he had at least half an eye on Tuesday night's EFL Cup quarter-final at Hull, and ultimately proved costly.
With so many alterations, Newcastle were understandably rusty in the opening stages, and the half-time interval arrived without the league leaders having recorded a single attempt on target.
Blackburn only managed one, and that arrived as early as the fifth minute, with Karl Darlow doing well to tip over Danny Graham's glanced header from Liam Feeney's right-wing cross.
Christian Atsu came close with a 29th-minute shot that was deflected wide at the front post, and Aleksandar Mitrovic directed an acrobatic volley over the crossbar four minutes before the interval, but Newcastle struggled to get anywhere close to the standards they had displayed in the majority of their previous outings this season.
Blackburn boss Owen Coyle will have been happy with his side's organisation and work rate, although Atsu should at least have forced a save from Steele when he volleyed Ayoze Perez's cross wide four minutes into the second half.
Isaac Hayden drilled a long-range strike narrowly wide of the target shortly after as Newcastle finally started to display some increased intensity, but Matt Ritchie wasted his side's best opportunity as he side-footed Paul Dummett's cross over the top from eight yards.
Blackburn's first chance of the second half chance came to nothing when substitute Marvin Emnes dragged a shot wide after wriggling free in the area, but while the visitors lived dangerously on a couple of occasions, they were always in the game.
They were indebted to their goalkeeper on two separate occasions inside a minute as Newcastle pressed for an opener, with Steele pushing Shelvey's long-range volley around the post before flinging himself to the ground to keep out Clark's stabbed effort after the Magpies centre-half turned inside the box.
Their tenacity was rewarded with 15 minutes left, though, as they claimed the lead. Mulgrew was the pick of the visitors' midfield all afternoon, and after a left-wing corner was flicked on at the front post, the Scotland international swivelled to hook home an excellent first-time volley.