Cottagers continue rise up the table at the expense of the Black Cats whose run without a league win stretches to six games despite Phil Bardsley strike in the first half.
The American international gave the Cottagers the lead with a splendid strike from a free kick for his 50th Premier League goal.
Martin O’Neill’s side drew level when Phil Bardsley fired a powerful effort past Mark Schwarzer after a good attacking move by the Black Cats.
This parity lasted only seconds as Dembele carried the ball from his own half before shooting at goal, and a deflection took the ball into the net to restore Fulham’s lead which was enough to give the team all three points as both sides mis-fired in the second half.
Martin Jol made one change from his side that beat Liverpool in midweek, as Mahamadou Diarra replaced Alexander Kacaniklic in the starting lineup.
Sunderland made three changes from the side that drew 2-2 with Bolton last week. Simon Mignolet replaced Craig Gordon in goal, while Ji Dong-Won and Craig Gardner came in for Fraizer Campbell and Nicklas Bendtner who both dropped to the bench.
The game started as scrappy affair as neither side was able to maintain possession for lengthy periods of the opening 10 minutes and chances were few and far between.
However, Fulham took the lead through Dempsey with a magnificent free kick as the American international curled an effort into the top corner from 25 yards placing the ball out of the reach of Mignolet after Lee Cattermole had fouled the Diarra outside the area.
The Black Cats responded and nearly got an equalizer through Stephane Sessegnon after a good move down the right, the 27-year-old latched skilfully beat Brede Hangeland before firing at goal but his shot was excellently saved by Mark Schwarzer.
Martin Jol’s side was beginning to take control of the game as the half wore on and could have gone further ahead if not for a superb block by Michael Turner as he denied Pavel Pogrebnyak whose volley looked destined for the net after being found by Damien Duff’s pinpoint cross.
Despite Fulham’s dominance in possession, O’Neill’s side got an equalizer through Bardsley who blasted a shot into the bottom corner after good build-up play down the left between Jack Colback and Ji, who found the fullback, unmarked, on the edge of the area.
Sunderland’s joy was short lived, however, as the Cottagers regained the lead just seconds after conceding. As Dembele drove at the Black Cats defense before firing a left-footed shot from 20-yards into the top corner with the ball taking a slight deflection on its way past Mignolet.
The Cottagers came out confident in the second half and nearly added to the lead five minutes after the restart but Dempsey’s goal-bound shot from the edge of the area was cleared off the line by Colback with Mignolet beaten.
Jol’s side was upping the ante looking to kill the game as Damien Duff raided down the right and cut inside beating Bardsley before firing a vicious left-footed shot at goal which was well saved by Mignolet who was quickly on his feet to scoop up the rebound.
The Wearsiders were trying to press the home side to get back into the game but lacked that final bit of quality in the final third to draw level. This was typified when Nicklas Bendtner fired a shot wide of the post after being put through on goal by Sessegnon with a lovely cross-field ball.
Sunderland should have drawn level in the 77th minute when Bendtner nodded the ball into Campbell’s path six yards from goal but the England man could only fire wide of the post much to the frustration of his teammates.
The Black Cats pressed for an equalizer but were unable to find a way through the Cottagers defense which put them at risk from Fulham counterattacks. Dembele nearly took advantage but he could only fire wide when one-on-one with Mignolet.
Sunderland came close late on through Campbell again but his effort was well saved by Schwarzer as the home side was able to hold out to secure the win.
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