Both Tony Capaldi, who signed for the Pilgrims in the summer and Peter Gilbert, who is on a three month loan deal, lined up for Argyle.
But it was Fagans temporary side who progressed to the second round. The Blues striker netted on 22 minutes with a headed goal from just inside the six yard box and despite Argyle equalising on 24 minutes, the Essex side scored again on 40 minutes and held that lead through to the end of the game.
Just a footnote - Fagan, Gilbert and Capaldi all picked up yellow cards!!
Elsewhere, it was a mixed night for two former Blues strikers. Paul Furlong was sent-off for a second yellow-card offence after just 21 minutes of QPR's 2-1 victory at Cheltenham (Tom Williams was an unused sub for Rangers) whilst Tommy Mooney scored a 73rd minute winner for his new side Swindon Town in their 3-2 victory at Southend United.
Blues go into the draw for the second round of the competition which takes place at 5.30pm this Saturday (16th August). Only the 8 Premiership sides competing in Europe are omitted from the next round which will be played week commencing 22nd September.