Sunderland boosted their automatic promotion hopes as goals from Kevin Kyle and Jeff Whitley secured the Black Cats a hard-fought victory over high-flying West Ham.
But the match was tainted by the news that Hammers midfielder Matthew Etherington had been taken to hospital with a suspected broken leg.
The former Tottenham winger took a knock in the 17th minute, after a clash with Stephen Wright and Whitley, and was immediately taken off for tests.
FA Cup semi-finalists Sunderland had three games in hand over the visitors going into the match, with boss Mick McCarthy anxious to make them count as the race for promotion hots up.
But they were playing host to a Hammers outfit full of confidence and with an eye for goal having put five past Wimbledon during the week.
Both sides displayed lots of honest endeavour but neither could fashion a shot on goal as the first half turned into a war of attrition.
Tackles were flying in thick and fast and just after the quarter-hour mark Etherington was forced off injured and replaced by former Manchester City stalwart Kevin Horlock.
Sunderland goalkeeper Mart Poom had been a virtual bystander for much of the opening period, but he was forced to warm his palms when Joel McAnuff caught a crisp 25-yard volley which the Estonian shot-stopper did well to hold on to.
The second period started in far brighter fashion with three good chances created within the opening five minutes.
Hammers striker Bobby Zamora rose to meet a McAnuff cross, but his close-range header was saved by Poom who also tipped over a 20-yard bullet from Marlon Harewood.
The hosts responded in kind and Tommy Smith saw his point-blank header fly straight into the arms of relieved Hammers keeper Stephen Bywater.
However, McCarthy's men were starting to gain control of possession and broke the deadlock on the hour mark.
A free-kick was lofted into the West Ham penalty area and Kyle stuck out his leg to slide the ball into the back of the net.
The visitors looked to respond immediately with both Michael Carrick and Nigel Reo-Coker seeing shots charged down by a committed Sunderland back-line.
And just as it looked the Hammers might pull themselves back into the match, Sunderland netted a second.
Christian Dailly failed to deal with a dangerous ball into the area and Whitley surged forward to fire home in the 76th minute.
With time running out West Ham boss Alan Pardew urged his side forward, but Sunderland held firm and clinched a crucial victory as they bid to return to the top flight.
Teams
Sunderland Poom, Wright, Breen, Babb, McCartney,
Oster (Piper 79), Whitley, Thirlwell, Thornton (Williams 86),
Kyle, Tommy Smith (Byfield 79).
Subs Not Used: Ingham, Kevin Cooper.
Booked: Whitley.
Goals: Kyle 61, Whitley 76.
West Ham Bywater, Repka, Melville, Dailly, Harley,
McAnuff (Deane 63), Harewood, Carrick,
Etherington (Horlock 18), Zamora, Reo-Coker (Nowland 82).
Subs Not Used: Srnicek, Ferdinand.
Booked: Horlock, McAnuff, Reo-Coker, Dailly, Repka, Zamora.
Att: 29,533
Ref: R Beeby (Northamptonshire).