There's a bittersweet feeling hanging over The Den this week. As the final whistle blew on Monday night, it marked not just the end of a match, but the close of a season that had so much promise for Millwall. The Lions fell 2-0 on aggregate to Hull City in the Championship play-off semi-finals, with second-half goals from substitutes Mo Belloumi and Joe Gelhardt sending the Tigers to Wembley and leaving Millwall to reflect on what might have been.

For much of this campaign, manager Alex Neil had a knack for turning games around with timely substitutions—turning defeats into draws and draws into victories. It became a hallmark of this Millwall side. But in the cruelest of ironies, it was Hull's bench that made the difference this time. Within a minute of coming on, Belloumi cut in from the left and curled a stunning opener past the helpless Millwall keeper. Suddenly, the Lions were trailing in the tie for the first time, and the momentum had shifted decisively.

Neil had already used three of his own substitutes by that point, introducing Barry Bannan, Alfie Doughty, and Mihailo Ivanovic in search of a breakthrough. But on this occasion, the magic didn't come. "It's been a great season," Neil told BBC Radio London after the game, "but at the moment all you feel is disappointment and frustration. You feel as if you've let people down—the supporters, the hierarchy. That's part and parcel of being a manager."

And yet, for all the heartbreak of falling short at the final hurdle, this has been a season of genuine progress for the Lions. Finishing third in the Championship table with 83 points, Millwall posted a total higher than the 82 points that secured the Second Division title in 1987-88 (albeit over a 44-game season). No team in the league kept more clean sheets than their 18, a testament to the defensive resilience that has become their trademark.

For the fans who packed The Den week after week, there is a quiet pride mixed with the disappointment. This was a team that dared to dream, that pushed a Premier League-ready Hull side all the way. And while the play-off dream may be over for now, the foundation is there for another run next season. As one former striker put it: "Gutted but proud." That sums up Millwall's campaign perfectly—a season of progress that ended in heartbreak, but one that has given the club and its supporters plenty of reasons to believe in what's to come.