"This will give us a lot of confidence," insisted Alan Pardew after seeing his side blow away the visitors with three goals in the final half-hour.
"At half time the fans would have been drinking their tea wondering about this team but hopefully they went away having seen our fight in the second half. We're working hard to get it together here."
Pardew's programme notes had called on the Upton Park faithful to be super positive after Tuesday night's dismal defeat against Stoke City.
But within just three minutes the club was back in the doldrums when Ian Pearce's woefully weak back header sold David James short and Marcus Stewart comfortably slipped around the advancing England keeper before inviting the supporting Jason McAteer to slot into an empty net from 12 yards.
Midway though the half John Oster curled a shot over the bar while at the other end David Connolly could not turn in the rebound after Defoe's 18 yarder hit the right-hand post.
On the half-hour, however, the marauding Marcus Stewart again caused both Pearce and James embarrassment following a goalmouth scramble. Oster pounced at the post to double the Black Cats lead.
Quite simply, Sunderland had too much movement for static West Ham who were lucky to retain 11 men when Tomas Repka escaped with only a ninth booking of the season following a heated bust-up with Julio Arca and the consequently cautioned Oster.
Following the restart Sunderland threatened to carry on from where they had left off, as Jeff Whitley soon rocked the bar from 18 yards.
But the introduction of Don Hutchison and Brian Deane suddenly gave West Ham the injection they so desperately needed.
In the 54th minute Deane's first touch saw him nod the ball into the path of Connolly whose shot was only parried by Mart Poom and Defoe gobbled up the rebound.
Indeed with 60 minutes on the clock, the previous hour was forgotten when Matthew Etherington's low centre was again swept home by Defoe from ten yards out to make it 2-2.
West Ham's sensational fightback was completed with ten minutes left when Kevin Horlock's touchline free kick was allowed to bounce off Poom's right-hand post to leave Pearce with an easy tap-in