Welsh midfield player Lloyd Humphries proved the matchwinner for Cardiff City in their Professional Under-23 Development League against Millwall in London.
Neath-born Humphries, aged 21 and a former Wales under-19 international, scored from a first half penalty to secure an away win for the Bluebirds.
The match at Millwall’s Calmont Road stadium saw former Cardiff team-mates Kevin Nugent and Andy Legg go head-to-head.
Nugent is Millwall’s under-23 coach, while Legg and Jarrad Harvey work together with the Bluebirds team.
The Lions included former Bluebirds goalkeeper Ben Amos in their starting line-up. Amos, who joined Cardiff from Bolton on loan in 2016-17, is 28-years-old and took up one of the over-age spots in the Millwall team.
Midfield player Stuart O’Keefe, back with Cardiff after a loan spell at Plymouth Argyle, started alongside new signings Danny Williams and Aaron Bolger, both making their full debut for the young Bluebirds.
They were sent on as substitutes at Coventry a week ago and were given the nod to start at Millwall.
Teenage striker Williams, aged 19, joined Cardiff from Welsh League Haverfordwest County where he had scored 18 league and cup goals this season.
Bolger joined Cardiff on loan from League of Ireland club Shamrock Rovers, a box-to-box midfield player who is 18-years-old.
He made 27 appearances, scoring one goal, including three matches in the Europa League.
Cardiff’s Dan Martin did well when he beat his marker and cross from the left with Ben Margetson going close.
Laurence Wootton was brought down by Millwall captain Harry Donovan after 25 minutes. Cardiff had produced a flowing move down the left and when Wootton took possession inside the penalty area Donovan stopped him with a rash challenge.
Humphries stepped up to score from the spot and that proved to be the only goal of the game.
Margetson and Williams, from a Wootton cross, both went close before half-time.
Chances were few and far between for either on a soggy afternoon, but the Bluebirds had the upper hand overall.
George Alexander forced Cardiff goalkeeper Matthew Hall into his first save after half-time, stooping to head goalwards from Junior Tiensia’s ball from the left.
Cardiff’s Joel Bagan almost scored with flicked header which went narrowly past a Millwall post.
Millwall force a scramble for possession in Cardiff’s six-yard box late on after smart work by substitute Reuben Duncan down the right.
Alexander’s improvised pass found Joe Wicks, but the midfield player was unable to fire off a shot with committed Cardiff defenders closing him down quickly.
Cardiff City’s under-23 team now have two successive home fixtures, against Queens Park Rangers at Cardiff International Sports Stadium on Monday, February 25 (1pm) and Sheffield United at Cardiff City Stadium on Monday, March 4 (7pm).
Millwall: Amos; Hanson, Debrah, Parker, Tiensia; Skalak (Mitchell 67), Donovan (capt), Wicks, Saunders-Henry (Harvey 78); White (Duncan 46), Alexander. Sub not used: Sandford.
Cardiff City: Matthew Hall, Ryan Pryce, Dan Martin, Lloyd Humphries, Ben Margetson, Joel Bagan, Laurence Wootton, Stuart O’Keefe, Dan Griffiths, Aaron Bolger, Danny Williams. Subs: Jac Davies, Warren Burwood (gk), Bowen, Sion Spence.