Two goals from super-sub Ben Wilson were in vain as Albion suffered a 3-2 defeat to Leyton Orient in their EFL Trophy opener at the Breyer Group Stadium.
Sam Ling and Dan Johnson scored either side of half-time to put the hosts in charge before Wilson produced two well-taken close-range goals in the last five minutes to make it 2-2.
A penalty shoot-out for the bonus point was looming, but in the fourth minute of stoppage time Connor Wilkinson won it for the hosts with a well-taken volley moments after Lee Angol had blazed a spot kick over the Albion bar.
The finale was harsh on Simon Rusk’s side, who got stronger as the game wore on but they may need to beat Charlton and AFC Wimbledon in their remaining group games if they are to progress to the knockout stages.
It was a strong Albion line-up with Jensen Weir and Lars Dendoncker making their competitive debuts after joining in the summer.
Orient fielded just two of the players who had opened their season with a 2-1 win over Forest Green Rovers in the Carabao Cup on Saturday and Ling - who was one of them - put them in front in the 35th minute.
Former Albion youngster Jordan Maguire-Drew swept over a free-kick from the left which Jamie Turley headed goalwards. Albion cleared as far as defender Ling whose header looped into the top right-hand corner.
It was just about deserved and Orient nearly doubled their lead four minutes into the second half when Maguire-Drew’s cross found Ruel Sotiriou but his header flashed wide of the left-hand post. A minute later Ling’s volley was only a yard wide of the same upright.
As the game finally sparked into life, Peter Gwargis had offered Albion’s best attacking threat and he was inches away from equalising in the 51st minute after cutting in from the right and hitting a right-foot shot which flashed wide with O’s keeper Sam Sargeant at full stretch.
Orient doubled their lead in the 55th minute with a superb goal by Johnson. He controlled a cross from the right, turned and struck a superb volley with power past Carl Rushworth and into the bottom corner.
Orient looked to be in cruise control but Albion hit back in the 85th minute when Peter Gwargis picked out substitute Wilson in the six-yard box and he showed good control before firing low past Sargeant. Moments later Stefan Vukoje stabbed a shot wide from a great position but Albion kept pushing and drew level in the 89th minute. Gwargis was the creator again with a lovely cross which found Wilson in space at the far post and he headed powerfully past Sargeant.
The drama wasn’t over. Rushworth produced a brilliant save at full stretch to turn Maguire-Drew’s powerful effort over the bar before Orient were awarded a controversial penalty in the second minute of stoppage time when Angol took a tumble in the box. To Albion’s amazement, the referee pointed to the spot but Angol’s penalty cleared the bar and the first six rows of seats in the stand behind the goal.
Just when it looked as if we were going to have a penalty shoot-out Orient snatched a last-minute winner.
Defender Jamie Turley headed a free kick back across goal and substitute Wilkinson pounced on the loose ball with a smartly taken volley inside the right-hand post.
It was harsh on the Seagulls, who will now start to prepare for Saturday’s Premier League 2 opener when they travel to Tottenham Hotspur.
Albion: Rushworth, Yapi, Roberts (Tsoungui 78), Dendoncker, Cochrane (capt); Spong (Wilson 58), Crofts, Jenks, Weir, Gwargis; Cashman (Vukoje 72). Unused subs: Leonard, Furlong, Tanimowo, Talley.