Goals from Tom Bradshaw and Aiden O'Brien secured Millwall's passage to the Second Round of the Carabao Cup on Tuesday night with a 2-1 victory at West Bromwich Albion.
Charlie Austin gave The Baggies the lead at The Hawthorns, but Bradshaw and O'Brien both converted from Jiri Skalak deliveries to win the game for The Lions and a place in the draw.
Neil Harris made eight changes from Saturday's corresponding fixture, with Murray Wallace, Ryan Leonard and Bradshaw the only survivors. Luke Steele, Jason McCarthy and Jayson Molumby made their Lions debuts, whilst there was also a first start for Jon Dadi Bodvarsson following his summer move from Reading.
An even opening saw both sides exchange possession in the middle, but the first chance went the way of The Lions on seven minutes - Bradshaw, however, fired wide after Bodvarsson's flick-on.
New Baggies signing Austin then headed on to the roof of the net, but he didn't have to wait long for his first goal in a West Brom shirt, as after Steele fumbled Grady Diangana's deflected effort, the striker was there to nod in from a couple of yards out to open the scoring.
Austin then attempted to lob Steele, but to no avail, before Kyle Edwards was next to try his luck, but the stopper had the effort covered.
Shortly before the half-hour mark, The Lions were level, as Skalak's superb delivery was powered home by the head of Bradshaw for his first goal in a Millwall shirt.
Two minutes later, West Brom had the ball in the net, but Semi Ajayi's header was ruled out for a foul. That nearly proved to be a pivotal moment in the game, however, as with 10 minutes to go until the break, debutant McCarthy's shot was saved at close range by Johnathan Bond, but the 'keeper bounced back up to tip Aiden O'Brien's spectacular goal-bound effort over the crossbar. After a duo of corner-kicks, Murray Wallace's header across goal found Bodvarsson, but the Icelandic's free header sailed over.
The Lions were now in the ascendancy, and had more corners in their attempts to nudge themselves into the lead, but a combination of a lack of finishing and a strong Baggies defence kept Millwall at bay.
With 55 minutes on the clock, Millwall were in front. Another inviting Skalak delivery fell to the back post, where O'Brien stabbed the ball home from close range for his first of the season.
Just after the hour-mark, a superb, lung-busting run from Leonard allowed The Lions to win a free-kick on the right-hand side, but the ball was cleared. Shane Ferguson, now playing as a right-winger after the introductions of Shaun Williams and Mahlon Romeo, then blazed over after cutting inside on his favoured left-foot with 25 minutes remaining.
With The Hawthorns restless and Millwall still on top, substitute Williams was presented with a chance after Leonard's header into the box saw the midfielder beat the offside trap, however he failed to make a proper contact with the ball.
Through four minutes of stoppage-time, West Brom tried to take the tie to penalties, but The Lions held firm to claim success on the road.
West Bromwich Albion: Bond, Furlong, Ajayi, Brunt, Townsend, Austin (Pereira 60'), Harper, Burke, Edwards (Krovinovic 60'), O'Shea, Diangana (Sawyers 70'). Subs not used: Johnstone, Willock, Fitzwater, N. Ferguson.
Scorer: Austin 9'
Millwall: Steele, McCarthy, M. Wallace, Hutchinson, Bradshaw (Thompson 79'), S. Ferguson, Molumby (Williams 62'), Leonard, O'Brien (Romeo 64'), Bodvarsson, Skalak. Subs not used: Bialkowski, Cooper, Mahoney, Smith.
Scorer: Bradshaw 28', O'Brien 55'
Booking: Hutchinson, Thompson
Referee: Ross Joyce
Attendance: 10,704 (388)