Newcastle United, the club Ba left on Friday, continued their dismal run of form with a 2-0 defeat at Championship (second tier) side Brighton and Hove Albion - a rare upset on one of the most eagerly-awaited days in the English season.
Goals from Andrea Orlandi and Will Hoskins earned Brighton a repeat of their fourth round victory over Premier League Newcastle last season, condemning Alan Pardew's side to an 11th defeat in 14 matches.
Major shocks were non-existent although Cardiff City, currently romping away at the top of the Championship, were beaten 2-1 at minor league Macclesfield Town - who reached the fourth round for the first time.
Minor league Luton Town also beat second tier Wolverhampton Wanderers 1-0.
Several clubs struggling in the Premier League flirted with defeats against lower league opposition but survived.
Fulham drew 1-1 at home to Blackpool, third tier Bournemouth earned a replay with Wigan Athletic after holding them to a 1-1 draw while Sunderland drew 2-2 at Bolton Wanderers who were relegated from the top flight last season.
Reading had to come from a goal down to beat third tier Crawley Town 3-1 away.
South coast seventh-tier minnows Hastings United, the lowliest survivors of the 758 clubs which began the 132nd edition of the knockout competition in August, had their fairytale cut short in a 4-1 defeat at Middlesbrough.
Premier League champions Manchester City, winners of the competition in 2011, eased into the fourth round with a 3-0 defeat of Gianfranco Zola's Championship side Watford.
Tottenham Hotspur's fine run of form continued with Clint Dempsey scoring twice in a 3-0 home victory over third tier Coventry City, the side they lost to in the 1987 FA cup final.
Premier League leaders Manchester United are in action later at West Ham United. (Reporting by Martyn Herman, edting by Mark Meadows)