Manchester City lost further ground on the Premier League pacesetters after dropping points against West Bromwich Albion on home soil.
After failing to beat Manchester United over the weekend, Pep Guardiola recalled the talented Phil Foden at the expense of Algeria international Riyad Mahrez.
The visitors looked lively early on as Darnell Furlong and Karlan Grant went close to breaking the deadlock in the early stages.
After failing to get the early goal, the Citizens had to wait until the 30th minute as Ilkay Gundogan found the back of the net with a neat finish from close range.
However, the Baggies managed to hit back five minutes before the break when Semi Ajayi's shot took a deflection off Ruben Dias before sailing into the net.
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The frustration began to grow for City in the second half and that was further compounded when Gabriel Jesus was forced off with an injury and replaced Sergio Aguero.
Even with Aguero on the pitch, the visitors defended with everybody back but it was goalkeeper Sam Johnstone who stole the show.