Newcastle United had an evening to forget at Hillsborough.
Rafa Benitez's second-placed side were beaten 2-1 in the Championship by Sheffield Wednesday.
Second-half goals from Tom Lees and Steven Fletcher saw off Newcastle, who were punished for an error-strewn performance.
Third-placed Huddersfield Town had been beaten 2-0 by Nottingham Forest at the City Ground earlier in the day, but United never looked like capitalising on that loss.
And they remain 10 points clear of David Wagner's side with five games left to play.
The defeat was compounded by the loss of leading scorer Dwight Gayle to injury in the first half.
Wednesday showed their intent early in the game by creating a series of chances against a wobbly visiting defence which again featured Chancel Mbemba.
Gary Hooper struck the crossbar, while Fletcher somehow put a shot wide in the 15th minute.
Barry Bannon was fortunate not to get a red card for a reckless challenge on Matt Ritchie later in the half, while Darlow did well to deny Fletcher after Mbemba gave the ball away on the byline.
Newcastle then lost Gayle to what could be another hamstring problem.
United's only real chance of the half came in added time when Shelvey, seeing Keiren Westwood off his line, struck the crossbar with an effort from the halfway line.
The visitors were better in the minutes after the break, and Shelvey forced a save with a free-kick.
But Newcastle's defensive frailties never really went away, and Lees headed a Ross Wallace free-kick home in the 59th minute.
Former Sunderland striker Fletcher got the better of captain Jamaal Lascelles to head a long throw-in past Darlow and make it 2-0 nine minutes later.
Shelvey netted late in the game after Westwood spilled a shot from substitute Aleksandar Mitrovic.
United, however, couldn't conjure up a late equaliser.
SHEFFIELD WEDNESDAY: Westwood, Hunt, Lees, Loovens (Sasso, 46), Pudil, Wallace (Semedo, 73), Bannan, Jones, Reach, Fletcher, Hooper (Rhodes, 59). Subs not used: Wildsmith, Winnall, Palmer, Forestieri.
NEWCASTLE UNITED: Darlow; Anita, Lascelles, Mbemba, Dummett; Shelvey, Diame (Atsu, 72); Ritchie (Mitrovic, 79), Perez, Gouffran; Gayle (Murphy, 29). Subs not used: Elliot, Gamez, Haidara, Ameobi.
Goals: Lees 59, Fletcher 68, Shelvey 88
Bookings: Bannon 19, Diame 45, Wallace 70
Referee: Stuart Attwell (Warwickshire)