Crewe Alexandra Under 18's were undone by a clinical Millwall side in London in the second long trip in the first three games for Lee Bell's side.
After triumphing 2-0 at Charlton in the season opener, the 18's lost 3-2 at home to QPR before the trip to The Lions.
Luke Offord got on the score-sheet for Crewe, but Millwall had already asserted themselves into a commanding position & on target for the three points.
The hosts took the lead early in the first half, Matt Neary tapping into the net from close-range to make the most of a team-mate's miss-hit shot.
A Mason Saunders-Henry penalty put the Lions 2-0 up at half-time after an Alex defender was penalised for handball.
Midfielder Harry Taylor got his first of the game shortly after the break for 3-0, before Offord grabbed his goal to reduce the deficit with a header from a swung in right-flank free-kick.
But Millwall pressed their advantage for the remainder of the game, adding gloss to the score-line via Ruben Duncan before Taylor capped off the scoring late on with his second.
Crewe: Booth, T.Johnson, Offord, Manuel (Heath), Adibisi, Lynch, Griffiths (Barlow), C.Johnson (Lomas), Hurst, Walsh, Thompson