ALBION were sentenced to their heaviest defeat of the season by a rampant home side who were spurred on by events elsewhere.
The Baggies trailed at the break to Sergio Aguero's sixth-minute opener but, although they struggled to trouble the City goal, remained very much in the game.
However, the landscape changed when news reached the Etihad Stadium that title rivals Manchester United were losing at Wigan.
Roberto Mancini's men smelt blood - and netted three times in ten minutes.
Aguero's second of the game on 54 - his 19th league goal of a stunning season - was quickly followed by further strikes from Carlos Tevez on 61 and David Silva three minutes later.
There was no lack of effort from the Baggies at Eastlands, but they were simply out-classed by City's expensively assembled side.
The Blues' defeat at Arsenal on Sunday may have left them eight points behind leaders United in the title race, but the Baggies still faced a monumental challenge.
Craig Dawson made his first Barclays Premier League start in three months as Roy Hodgson rang five changes. Also recalled were Paul Scharner, Shane Long, Nicky Shorey and Simon Cox, with injured duo Liam Ridgewell and Chris Brunt (both knee), plus benched trio Gareth McAuley, Peter Odemwingie and Marc-Antoine Fortune, making way.
On the bench, young winger Kemar Roofe made a Premier League squad for the first time, where he was joined by another Academy graduate, James Hurst, following his recall from a loan spell at Chesterfield.
Albion's much-changed team settled into the illustrious Eastlands setting quite nicely and, following neat build-up play, Cox recorded the first shot of the game after just 67 seconds, although his 20-yard strike failed to trouble Joe Hart's goal.
However, within a minute, the hosts underlined what they are capable of and it took a fine block by Billy Jones to prevent Aguero's 15-yard effort giving Ben Foster an early save to make.
Very little else happened - until City surged 1-0 up in the sixth minute.
Aguero collected the ball just inside the Albion half and remained unchallenged as he let fly from 25 yards, giving Foster no chance with a right-foot rocket which nestled in the bottom-far corner.
City looked full of purpose and a slick interchange between Samir Nasri and Tevez created a shooting opportunity for the latter on 11, but he was well off target from the edge of the box.
However, Albion were far from being overawed, with Long looking lively in his lone striker role. The trouble was, the Baggies' attacks kept getting smothered by the Blues' dominant defence.
And it was City who threatened next. On 22, the recalled Silva exchanged a clever one-two with Tevez before firing straight at Foster from the tightest of angles.
Four minutes later, Keith Andrews did well to get in the way of Gareth Barry's 20-yard drive from Aguero's pull-back.
Albion produced their best moment thus far on 29 when a sweeping move started by skipper-for-the-night Jonas Olsson at the back resulted in Cox flashing a ball across the face of goal, which just evaded the lurking Long.
Less than a minute later, the third member of Albion's Republic of Ireland triumvirate, Andrews, directed a fierce 25-yard shot straight at Hart.
But Albion had a real let off on 31.
Micah Richards bustled past Shorey to get on the end of Tevez's defence-splitting pass and after rounding Foster, the right-back saw his shot deflected wide of the gaping net by Dawson.
The remainder of the half proved a non-event, with Albion comfortably seeing off the little City threw at them. Chances at the other end remained at an absolute premium, though.
After a low-key start to the second half, City suddenly burst into life on 49 through Silva's jinking right-wing run. The Spanish international picked out Nasri in the box and the former Arsenal ace blasted a fine volley into the side-netting from a difficult angle.
Dawson was having an impressive game but his evening became an extremely painful one when he took a thunderous Silva shot square in the face on the edge of the Albion box. Thankfully, after treatment, the former Rochdale centre-half was able to continue.
But as news filtered through that neighbours United were losing at Wigan, the home crowd found their voice - and their team responded by surging two-up on 54.
City seized possession of the loose ball on the edge of the Albion box and Nasri slipped in Aguero, who calmly slotted past Foster from 15 yards.
Moments later, Nasri advanced onto Tevez's lay-off and shot just wide of the far post from 18 yards.
Albion briefly earned some respite from the City pressure through a foraging Cox run, which resulted in Graham Dorrans having a shot from just inside the box deflected wide
Back came City and after Dawson, twice, and Youssouf Mulumbu made vital interceptions in the Albion box, City went 3-0 up on 61.
Aguero raced to the Baggies' by-line and pulled the ball back for Tevez, whose 12-yarder clipped Jones on the way into the net.
Albion handed City their fourth on a plate. On 64, the usually-dependable Olsson was dispossessed by Ageuro deep in his own half and the Argentina ace slipped in Sliva, who beat the on-rushing Foster with the most sublime of chips.
The Baggies did manage to stem the City tide but only briefly, and Aguero went close again on 71 when his acrobatic header from sub Adam Johnson's centre looped onto the roof of Foster's net.
However, Albion did go close on 74. Long was denied a simple tap-in by Vincent Kompany's last-ditch interception after a terrific run and low cross from sub Fortune.
From Dorrans' ensuing corner, Scharner directed a free header over Hart's bar.
Fortune went close again three minutes from time when he drilled into the side-netting from a tight angle.
MAN CITY (4-2-3-1): Hart; Richards, Kompany, Lescott, Clichy; de Jong, Barry; Silva (Zabaleta 80), Nasri, Tevez (Johnson 63), Aguero (Dzeko 74). Subs not used: Pantilimon (gk), Kolarov, Milner, Pizarro.
ALBION (4-5-1): Foster; Jones, Dawson, Olsson, Shorey; Cox, Scharner, Mulumbu (Fortune 69), Andrews, Dorrans (Tchoyi 78); Long. Subs not used: Daniels (gk), McAuley, Odemwingie, Hurst, Roofe.
GOALS: CITY - Aguero (6 & 54), Tevez (61), Silva (64).
REFEREE: K Friend (Leicestershire).
ALBION STARMAN: Graham Dorrans.