Sunderland's promotion bid suffered another setback as they were held to a damaging 1-1 draw by relegation-threatened Gillingham and booed off at the Stadium of Light.
The inactivity of second-placed Wigan had given the Black Cats the opportunity to steal a march on their rivals by edging two points above them.
But despite fielding an adventurous three-pronged attack, Sunderland's promotion credentials will again be questioned after they failed to bounce back from their New Year's Day defeat at Preston.
The visitors took the lead in the 14th minute when the former Sunderland striker Darren Byfield teased and tormented the home defence before crossing for Darius Henderson to head home.
That lasted just four minutes, however, as Sunderland left-back George McCartney embarked on a run past three defenders before he crossed low for Chris Brown to turn in at the near post.
The impressive Byfield had almost opened the scoring earlier than he did when Dean Whitehead's undercooked back-pass allowed him to collect the ball on the edge of the penalty area before a combination of keeper Thomas Myhre and defender Gary Breen kept him out.
The mistake jolted the hosts into life as they immediately tore upfield where Marcus Stewart played Sean Thornton in. The former Tranmere man matched the pass with an emphatic finish but the effort was ruled out for a marginal offside.
Inspired by the tigerish Andy Hessenthaler, however, Gillingham continued to battle and with Byfield and Henderson in attack, they possessed a dangerous goal threat. With little over 20 minutes remaining Michael Bridges replaced Brown but made little impact for Sunderland.
Gillingham had the best chances to win but Richard Rose fired over from a Matthew Jarvis pass, while another Gillingham counterattack saw the on-rushing Byfield inexplicably fail to connect properly with a ball played across the goal.
Sunderland: Myhre, Wright, Breen (Neill Collins, 42), Caldwell, McCartney, Thornton, Whitehead, Whitley (Piper, 58), Stewart, Elliott, Brown (Bridges, 68). Substitutes not used: Welsh, Alnwick.
Gillingham: Banks, Rose, Smith, Ashby, Hills (Jarvis, 29), Southall, Hessenthaler, Crofts, Cox, Henderson (Roberts, 78), Byfield. Substitutes not used: Bossu, Bodkin, Beckwith.
Referee: M Atkinson (W Yorkshire).Reuse content