Scorers: Manchester City - Negredo (12, 26, 49) Touré (40), Dzeko (60, 89)
Edin Dzeko grabbed two and Yaya Toure also got on the scoresheet as City all but booked a trip to Wembley by piling on the misery for the Hammers and their under-fire manager Sam Allardyce.
City needed just 12 minutes to take the lead at the Etihad Stadium and the Londoners were simply swept aside in an embarrassingly one-sided match.
Allardyce, who was taunted by visiting fans late in the game, had prioritised the game to some extent by fielding a weakened side against Nottingham Forest in the FA Cup third round last weekend.
But that backfired as they were thrashed by six goals and despite eight changes, including the return of senior players such as Mark Noble, Joe Cole, Guy Demel and Mohamed Diame, it proved a similar story in the Manchester rain.
West Ham were troubled in the opening moments as Samir Nasri cut open their defence and Toure crossed looking for Pablo Zabaleta. The Argentinian was denied a shot but the ball rebounded and Adrian needed to keep out a ricochet off Negredo.
City took the lead as Toure, with plenty of time in the centre of the field, picked out Negredo with a superb long ball.
The Spaniard’s technique was equally brilliant as he allowed the ball to drop over his shoulder before lashing a powerful left-foot volley into the bottom corner.
After that it seemed all too easy for City as Toure robbed Mohamed Diame to launch a raid that led to David Silva and Nasri testing Adrian from long range in quick succession.
City doubled their lead after 26 minutes as Negredo latched on to a fine ball from strike partner Dzeko and confidently drove across Adrian into the top corner.
City continued to bombard the beleaguered visitors as Dzeko twice fired over and Negredo also missed the target.
Toure then charged through the back-tracking Hammers defence with alarming ease to poke home City’s third five minutes before the interval.
Allardyce sent on Carlton Cole for the second half in an attempt to give his side more shape and firepower but it made little difference.
Negredo completed his hat-trick within four minutes of the restart as he curled a shot past Adrian after Dzeko and Silva had combined.
Toure then fired over from a free kick and Dzeko sent a long-range effort narrowly over the bar. Silva then cut them open again with a cross-field pass for Gael Clichy and the Frenchman’s cross was slid home by Dzeko for 5-0 on the hour. That marked the end of Toure’s work for the night as manager Manuel Pellegrini started to look ahead to the weekend trip to Newcastle.
Adrian produced another good stop to deny Dzeko but it merely stemmed the tide as the Bosnian thumped in City’s sixth from an Aleksandar Kolarov cut-back a minute from time.
Referee: J Moss