Edin Dzeko struck twice after his 79th-minute introduction as a substitute, the second of which came deep into injury time, as 10-man Manchester City defeated West Brom 2-1 at The Hawthorns in the Premier League.
City had won only two of their previous seven games in all competitions and their problems deepened on 23 minutes as James Milner was shown a straight red for bringing down Long following a terrible piece of play from Vincent Kompany.
Though City dominated for long spells despite the dismissal, it was West Brom who took the lead when Long latched on to a mis-hit shot from Peter Odemwingie and produced an intelligent finish to guide the ball past Joe Hart.
At that stage the Baggies were set to overtake City and claim third place in the Premier League after eight games of a remarkable season under Steve Clarke, but Dzeko was summoned from the bench and within 60 seconds had equalised, exploiting a poor piece of goalkeeping from Ben Foster.
It was the striker's third goal as a substitute this season - more than any other player - and he was not finished, the Bosnian converting with a fine first-time finish in a frantic period of injury time as City hit West Brom on the break to snatch a 2-1 win and stay level with Manchester United in second place.
Having won their first four home games of a top-flight league season for the first time since 1919, it came as little surprise to see West Brom start confidently and after only 19 seconds they registered the first chance of the game as Marc-Antoine Fortune, in for Odemwingie, fired a low effort just wide of the far post from 20 yards.
Neither side possessed genuine width so a congested midfield battle unfolded which initially left little room for goalmouth action. An abrasive contest instead took on a physical dimension as Mario Balotelli and Yaya Toure became involved in a succession of incidents, with the Italian one of four players booked in the first half with a particularly silly push on the back of Claudio Yacob.
A running battle with Gabriel Tamas also threatened to bring out the worst in the tempestuous Italy international but Balotelli was also at the heart of everything City produced in the final third, one low effort early on forcing Ben Foster into a smart save after Balotelli had cut in from the left to lose Tamas.
Balotelli then produced a gorgeous first touch to pull down a cross-field pass, finding Carlos Tevez with a cross that enticed the striker into turning an ambitious volley wide at the near post, and the Italian was irrepressible at times, another fine piece of skill taking him between two men before he tested Foster with a fierce low effort.
Micah Richards also saw a header turned over the bar by the West Brom keeper, but City's attempts to control the game were undermined after 23 minutes when Milner was dismissed.
Kompany was at fault when wandering out of defence and losing possession in uncharacteristically sloppy fashion and when James Morrison played a pass through the centre of the pitch for Long to run onto, Milner brought him down as the last man. Joleon Lescott was in close attendance, but would not have prevented Long from having a shot and Mark Clattenburg was correct to wave the red card.
West Brom struggled to take advantage - a firm drive from Yacob and a hopeful volley over the bar from Morrison their two best chances of the half - yet City went perilously close to giving them an ever greater numerical advantage when Balotelli, already booked, had stern words with Clattenburg after fouling Long and then again when he harangued the referee as he walked off for half time, City still angry with the official's failure to give a penalty when in fact Fortune handled just outside the box.
City exerted an even stronger grip on the game immediately after the break, with Foster forced into a tremendous save soon after the restart as he flung out an arm to palm away a stunning effort from Tevez following a square pass from Balotelli. The Italian then drove in from the right of the box to cut the ball back into open space, with Gael Clichy arriving with a thumping drive that caught the chest of Tamas.
After 59 minutes they should really have been in front. A Tevez free kick was headed back across goal by Micah Richards but after Balotelli swing and missed, the ball bounced up perfectly for Toure. Foster was out of position and the midfielder had only to head into an empty net, yet he managed to send the ball spinning over the bar.
City were punished for their failure to capitalise on the pressure they exerted on West Brom when the home side took the lead through Long after 67 minutes. Odemwingie, on as a substitute, was guilty of a weak shot at goal but Long timed his run to perfection to nip in behind Kompany and meet the ball with a gorgeous finish with his instep as he slipped his shot past Hart and inside the post.
Mancini responded though and on 79 minutes made the substitution that would change the game. On came Dzeko and within a minute he had City level when guiding a Tevez free kick home as Foster came and failed to punch the ball away.
A breathless final 10 minutes saw both sides go for a winner, with West Brom substitute Romelu Lukaku enjoying a number of clear-cut chances, the most audacious of which saw the Belgian execute an overhead kick that forced Hart into a smart save. However, from the corner West Brom were punished on the break as City raced away and Aguero played a square pass for Dzeko, the striker dispatching an accomplished finish out of the reach of Foster.
Still West Brom could have had a second goal - Lukaku threatening once again - but their proud home record was surrendered to a Dzeko-inspired City.
MAN OF THE MATCH
Edin Dzeko - Manchester City: He may only have been on the pitch for 10 minutes but the striker transformed this tie, scoring twice to hand Manchester City a very welcome win. Both finishes were top class and he almost grabbed a hat-trick too.
WEST BROM: Foster 5, Tamas 6, McAuley 6, Olsson 6, Ridgewell 6, Mulumbu 6, Yacob 7, Dorrans 6, Morrison 7, Fortune 5, Long 7. Subs: Odemwingie 7, Gera 6, Lukaku 6.
MANCHESTER CITY: Hart 6, Richards 6, Kompany 5, Lescott 7, Clichy 6, Milner 5, Barry 6, Toure 7, Nasri 5, Balotelli 7, Tevez 6. Subs: Aguero 7, Dzeko 8, Kolarov 6.