Noel Hunt's Reading Under-21 side dropped out of the top five of the Premier Development League with their second loss of the season, going down 2-1 to Cardiff City.
Substitute Adrian Akande pulled one back for the Royals in the final 10 minutes, but the damage had already been done in the Welsh capital.
Unlike last week, the squad was not full of experienced pros, like Andy Carroll or Yakou Meite, with Paul Ince being forced to include a few regular youth players in his first team due to injuries.
Jahmari Clarke, who has two Championship goals to his name from last seasons 2-1 win over Birmingham City, saw a chance go begging but the Bluenirds took the lead on the 20 minute mark with Tom davis tapping in at the near post.
Rashawn Scott, who made his first team debut on the final day of last season, was a threat throughout and his the crossbar just before half-time.
Basil Tuma, who played in the Carabao Cup in August, saw his effort drift across the open goal after the keeper dropped a free kick.
The Royals improved after the break, dominating possession, but just couldn't manage to put the ball in the net.
A well-worked corner left Louie Holzman with a strike on goal, which was well blocked, before Akande made it a nervy ending by pulling one back.
Clarke, who cut a frustrated figure throughout, saw red as the mist descended and the striker needlessly swiped out at his defender.
The win lifts Darren Purse's Cardiff level on points with Reading in the Professional Development League.
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