The scoreline flattered Reading, who went into the cup clash unbeaten in 11 gamesbcfc.com
And it was a scoreline that somewhat flattered their opponents, at Woking FC.
Indeed, the decisive breakthrough didn't come until the 64th minute, ironically after a spell of dominance by Blues once the second-half got underway.
But Tyler Frost's goal - the first of a hat-trick, which then included two penalties - really put the dampeners on Blues efforts to that point.
Frost completed his treble in added-time from the spot, but it was a ridiculous decision to award the penalty as it was, Ben Forrest's sliding tackle on Ben House was perfectly fair.
Craig Gardner gained extra match action minutes for Blues, and he was an influential figure spraying passes around and dictating play in particular during the strong spell when Reading were put onto the back foot.
Josh Andrews had two good opportunities for Blues before the interval and had those gone in, it might have been a different story in this Group G fixture.
Reading came into the tie unbeaten in 11 matches and Connal Trueman, also included to get some minutes under his belt, made a good early stop from House, who caused a fair few problems initially.
But in the 23rd minute, from a Gardner corner, Andrews came in round the back of a cluth of players jostling to connect, and went up too early, resulting in the ball catching him in the upper chest and rebounding to the 'keeper.
Trueman made a sharp stop to deny a Frost shot at the near post before Geraldo Bajarmi - who anchored Blues defence increasingly impressively as the match wore on, making some timely clearances and interceptions - headed just wide of the top corner, from another
In added-time, Andrews rose highest to meet Gardner's corner but glanced his header down and wide from a very good position.
Blues came out in the second-half and were brimming with intent and purpose. The put an extended period of pressure on the Reading defence.
But, with their first meaningful attack that gave them respite, the Royals caught Blues for once out of shape and played in Frost down the middle and he strode on into the area to fire past Trueman.
Olly McCoy stung the hands of the 'keeper, who tipped his shot over, as Blues responded.
Gardner was withdrawn in the 69th minute, along with Tommy Anderson; Josh Martin and Kyle Hurst entered the fray.
Unfortunately, Blues went further behind after Cameron McGilp's scything challenge on Teddy Lowe resulted in a penalty. Frost sent the wrong way, his spot-kick squeaking in off the post (73 minutes).
George Baker made his return from injury as a substitute and it was his cross from the right that had Reading's defence scrambling danger away, with a good block on Bajrami's close range effort.
Blues, who lost their opening Premier League Cup game to Fulham, were hard done by in the third minute of added-time when Forrest stopped House in his tracks to divert the ball for a corner; not so, according to the referee, who incredibly pointed to the penalty spot, allowing Frost to sidefoot home for his hat-trick.
Blues: Trueman, Forrest, Burke, McGilp, Bajrami, Redmond, McCoy, Craig Gardner (Martin 69), McFarlane, Andrews (Baker 85), Anderson (Hurst 69).Subs not used: Concannon, Luyambula.