Mick McCarthy's fringe players gave their manager food for thought ahead of their next Premier League game by putting four unanswered goals past Town.
Ebanks-Blake (2), Milijas and Vokes did the damage in front of over 5,000 at Sixfields as Northampton failed to repeat last season's League Cup heroics.
Attention now turns to a big League Two clash with Morecambe on Saturday.
"The scoreline is disappointing," said an upbeat Cobblers manager Gary Johnson afterwards.
"They have quality and a Premier League mentality but we matched them for much of the game and could have been one or two up.
"Nobody wants to hear that when the score is 4-0. But we were up against a good team and we will learn from it."