In the night's other matches, Leicester knocked out Walsall on penalties after a 0-0 stalemate and Aston Villa edged past Wycombe 2-1.
Chelsea thrash Barrow
It was an evening to remember for Chelsea's Christopher Nkunku, who bagged a quick-fire double in the first period of the Blues' clash with Barrow before completing his hat-trick in the 75th minute.
Pedro Neto, a summer signing under Enzo Maresca, also got in on the scoring in the second period, after Barrow's Paul Farman found his own net.
Manchester City edge Watford
For Manchester City, Jeremy Doku opened the scoring after just eight minutes to set the tone of their match against Championship side Watford.
Matheus Nunes - Neto's former teammate at Wolves - bagged his first goal for the Citizens a handful of minutes before the players went in at the break.
Watford scored a consolation goal through Tom Ince in the final stages, but the reigning Premier League champions never really looked threatened.
