Newport's Cameron Evans scored four times last season but was denied in a scramble
Millwall avoided a Carabao Cup upset after beating Newport County 1-0 at Rodney Parade thanks to Ryan Leonard's second-half strike.
The Championship club edged out their determined League Two hosts thanks to the right-back's powerful finish on the hour.
The Lions pushed for another - and were denied by three excellent saves - but one goal was enough to deservedly progress.
Both managers made sweeping changes from their weekend wins, with Newport fielding three starters from the side that faced Crawley Town and Millwall just two from their game with Norwich City.
The Exiles made a bright start with Bobby Kamwa just failing to get onto a long ball and Cameron Antwi missing the target from a well-worked corner move, before Millwall's Macauley Langstaff was denied by a timely Anthony Glennon block.
Newport were agonisingly close to opening the scoring in the 17th minute when James Clarke's header was smartly stopped by Max Crocombe, which was followed by an almighty scramble in the box.
Millwall gradually got on top and got their noses in front on the hour when the impressive Aidomo Emakhu broke down the left and cut the ball back for Leonard, who comprehensively beat debutant home goalkeeper Jordan Wright into the top right corner.
Newport's stopper then superbly denied Langstaff on the turn and Emakhu twice, but the League Two side could not conjure a leveller to force penalties.
Neil: 'We got stronger and stronger'
