Leroy Sane's brace gave Manchester City a battling 2-1 win at West Brom in the third round of the EFL Cup, but victory came at a price as Ilkay Gundogan was hit by another possible injury blow.
Sane has been restricted to one Premier League start so far this season, the odd-man out in Pep Guardiola's gifted forward line, but he grasped his chance with aplomb at The Hawthorns.
The 21-year-old's early opener preceded a swashbuckling first-half showing from a City side performing in the same vein as the recent romps against Liverpool, Feyenoord and Watford despite Guardiola making eight changes.
West Brom imposed their will on the match after the break, with the sight of Germany midfielder Gundogan – making a first start since tearing his anterior cruciate ligament last December – limping off following an ugly lunge from Claudio Yacob, noticeably unsettling City.
Yacob warmed to his role as villain by snatching an equaliser but the winner arrived against the run of play in the 77th minute, with Sane collecting Bernardo Silva's pass, cutting inside Craig Dawson and curling home past the excellent Ben Foster.
City controlled the action from kick-off, with West Brom's first touch of the ball coming when goalkeeper Foster denied Gundogan from Raheem Sterling's third-minute cross, with Sane on hand to smash home the rebound.
Gundogan was at the heart of much of City's impressive work early on and found space inside the West Brom box once more in the 18th minute, only for returning West Brom centre-back Gareth McAuley to make a vital block.
City took the resulting corner short, catching West Brom napping, and Sane chipped to the back post, where Foster palmed away Eliaquim Mangala's header.
Full-backs Fabian Delph and Danilo came infield to bolster a 26th-minute City attack and the latter picked out fellow Brazilian Gabriel Jesus, who engineered room in the box before blasting over.
Foster excelled himself in first-half stoppage time, clawing a curling effort from the rampaging Sterling away from his top corner.
Guardiola's only complaint over City's first-half efforts would have related to them not having a more commanding lead for their dominance and West Brom forward Jay Rodriguez glanced a Dawson cross wide early in the second period to underline the precariousness of their position.
City were enduring their most ragged period of the contest when, in the 54th minute, Gundogan broke up a West Brom attack and surged forward. His run was halted on the edge of the opposition penalty area, with Yacob booked and Gundogan unable to continue.
Foster remained on top in his personal duel with Sterling as the England winger's latest menacing dribble went unrewarded but James Morrison prodded wide at the other end, some excellent hold-up play from Hal Robson-Kanu fashioning a 69th-minute opening.
Guardiola's men did not heed that warning and Yacob, already far from popular with the travelling supporters, was allowed too much room to dispatch Kieran Gibbs' corner through Claudio Bravo's legs.
Robson-Kanu fired wide and Bravo saved from Morrison as West Brom suddenly appeared the likely victors, but Sane stepped up to brilliantly settle matters.
West Brom ensured their opponents made anxious progress towards full-time, with Salomon Rondon heading agonisingly wide from a Matt Phillips cross before Robson-Kanu clipped the outside of the post in stoppage time.