Stephen Wright’s 90th-minute own goal handed Pompey a lifeline and sent their third-round replay into extra time after Leon Best’s superbly-taken half-volley had broken the deadlock midway through the first half.

But the 2008 winners recovered from a lacklustre opening 45 minutes and were kept at bay by Sky Blues keeper Keiren Westwood before substitute Mokoena headed home with virtually the last touch of the game.

His goal set up a clash against Sunderland at the end of the month, but Coventry will feel extremely hard done by after a decent display by the Championship side.

The reward for Pompey is the visit of Sunderland in the fourth round later this month.