Brad Guzan's third-minute howler has gifted Manchester City a 1-0 half-time lead over Aston Villa at the Etihad Stadium.
Sergio Aguero pounced on the goalkeeper's scuffed pass to go to the top of the Premier League scoring charts with 21 goals.
The American was trying to find Jores Okore across his own box when his miscue fell to Aguero to tap home from 10 yards.
Another Guzan error could have cost Villa further when he flapped at a free kick which Fernando headed a few yards wide.
The self-destructing visitors nearly gifted City a second when Aguero latched on to Leandro Bacuna's stray back-pass, only for several Villa defenders to snuff out the danger which ceased when Jesus Navas's shot was blocked.
The FA Cup finalists, who are only two points above the relegation zone following this afternoon's results, improved after the half-hour mark and would have been level had Joe Hart not blocked from Christian Benteke after the in-form striker broke the offside trap.
