Double is just the start of the journey for evolving Bayer Leverkusen

<span>Xabi Alonso has turned down the chance to leave <a class="link " href="" data-i13n="sec:content-canvas;subsec:anchor_text;elm:context_link" data-ylk="slk:Bayer Leverkusen;sec:content-canvas;subsec:anchor_text;elm:context_link;itc:0">Bayer Leverkusen</a> in order to help the club win more trophies.</span><span>Photograph: John MacDougall/AFP/Getty Images</span>

It wasn’t supposed to happen like this. They had shown they could fall with the finishing line in sight – and how – to Zinedine Zidane’s famous, thunderous left-footer at Hampden Park, or to a rampant Bayern Munich in the mid-Covid DFB Pokal final in Berlin. For a more modern twist you could even throw in last year’s Europa League semi-final under Xabi Alonso’s command, in which José Mourinho and Roma miraculously survived a barrage in the BayArena (23 Leverkusen shots to Roma’s one). Not this season, though.

The greatest testament to Bayer Leverkusen’s extraordinary season is that losing Wednesday’s Europa League final in Dublin (and comprehensively at that) to Atalanta felt like the shock, rather than Die Werkself getting there in the first place to fluff their lines. Fifty-one games unbeaten up until that point doesn’t quite do it justice. Alonso’s side have been a juggernaut, trampling all in their way and, on the occasions they have found themselves behind, eventually reeling in their opponents with increasing inevitability. The later-than-late equalisers and winners against Stuttgart, Borussia Dortmund, Qarabag, Roma – the list goes on on – had the feel of one of the giants of Europe making gravity count, rather than an upstart, first-time champion, as they were in this season’s Bundesliga.

Related: European football: Xhaka seals double for Leverkusen; PSG clinch treble

If we say that “it” shouldn’t have happened, we mean what Stephan von Nocks described for Kicker as “a collective power outage” in the Aviva Stadium against Gian Piero Gasperini’s rampant side. Why we should really be pinching ourselves is in reaction to a season that has way outstripped the wildest of daydreams, let alone any reasonable expectation. Leverkusen have gone from a team to be enjoyed and lightly patronised, a simulation of elite-level football, a rehearsal for the big time before the real thing comes along for their best players at Bayern, Dortmund or wherever else, to the ogre, the irresistible, the tide you can’t hold back. They have transformed Germany’s and the continent’s expectations of them, and their expectations of themselves.

So if the second-tier strugglers Kaiserslautern might have normally benefited from popular support in Saturday’s Pokal final (“And I’ve never been more of an underdog in my career than in this game,” said their 70-year-old coach, Friedhelm Funkel, in the days leading up to the match), that felt less like the case this time. It felt as if Leverkusen deserved to complete the double for everything they have done in this unbelievable season, rather than it end in a whimper with successive defeats in finals.

For if an unbeaten Bundesliga season had never been achieved before, the loss to Atalanta had threatened to sour it. “It was not Bayer-like,” the midfielder Jonas Hofmann lamented, underlining how standards have risen. Granit Xhaka, Alonso’s surrogate persona and voice on the field, spoke for all the squad off it. “The disappointment is huge,” he admitted after full time in Dublin. He also challenged his team to show what they were really made of. “Now we have to see what character this team really has,” he continued. “When you’re unbeaten for 51 games, it’s easy to stand by each other. Now the time has come to see which player has character, which player can get up quickly and carry on. This defeat must not ruin our season.”

It was not just the first defeat, and the chances of going an entire competitive season undefeated dissolving into thin air at the last, but the manner of it. Hassled, harried and hurried like never before this season, Leverkusen were forced into slackness and imprecision at the end of a campaign characterised by their constant control, and by an Atalanta team using some of their opponents’ and supposed betters’ best moves, staying fresh by using their bench expertly, in recent weeks as well as in the final itself.

Berlin, then, became a battle with their own emotions for Leverkusen. The former star Michael Ballack, a mainstay of the 2002 side that blew a treble in less than a fortnight, put the feelings of many into words when he suggested that they “can only beat themselves”, referring perhaps not just to the quality gap between his old club and to Kaiserslautern, but to the need to respond to what happened in Dublin. The question shouldn’t have been there after this season, after all they have done and been through, but it was, and in more than whispered voice. What if we, as a club, haven’t really changed?

Certainly it was clear they were taking no chances in the final. Lukas Hradecky was restored in goal after Matej Kovar had played 17 of the 18 previous cup games, domestically and in Europe, with the tougher, more physical Robert Andrich and Patrick Schick drafted into the XI as well. What Leverkusen got in the end was maybe not the win they wanted, but the one they needed.

The value of Hradecky’s recall was shown in the first five minutes, as the Finn sprung to his right to parry away a fierce shot from Daniel Hanslik. The assurance it gave his team was palpable, and from there – especially after Xhaka’s goal, a trademark rocket from range almost passed into the top corner of the net – they briefly threatened to run riot in the manner many had expected from the moment Leverkusen trounced Fortuna Düsseldorf in the semi-finals in the opening days of April. Alonso’s reaction to the goal spelt out the relief in the camp too, the coach often so circumspect but running down his technical area and jumping to punch the air, a nod to his celebration in Lisbon in 2014, running on the pitch to hail Sergio Ramos’s last-gasp equaliser for Real Madrid as he sat out the Champions League final against Atlético Madrid through suspension.

It turned out to be not quite that easy, with a harsh second yellow card for Odilon Kossounou on the brink of half-time leaving the champions a man down, their first red of the season in its final game. As he has so many times this season, Alonso reshuffled at the break and Kaiserslautern were kept at arm’s length with relative comfort, even if the second goal never arrived. The celebrations that began on the field at the Olympiastadion on Saturday night continued on in a packed BayArena on Sunday.

When that well-deserved party dies down, or perhaps even before, Alonso will start planning for what is next. The club’s managing director, Fernando Carro, made clear that Leverkusen already have their sights set on even bigger and better, telling the players on the field in Dublin at full time to learn from the experience “for the Champions League final next year in Munich”. Alonso has not chosen to stay to mark time or to weigh up his future options. With Bayern Munich in a state of flux on the pitch and in the boardroom, there is an opportunity for Leverkusen to tighten their grip domestically. The plan is to keep the squad together this summer and with Alonso sticking around (and the star playmaker, Florian Wirtz, extremely likely to follow suit), it should be easier to do so.

The performance in Berlin might not have been the all-singing, all-dancing lap of honour that many expected from Leverkusen in the final. What it was instead was Alonso’s side showing how they are about graft as much as craft, constantly adapting and evolving to find solutions as they have done to astonishing effect all season. They are true champions. And they plan to keep it that way.