It only took one night against a Premier League power to suggest one of San Siro’s twin tenants cannot win the Champions League. AC Milan have a glorious past and, after three minutes, they led Liverpool. Some 90 minutes later, it was apparent the Rossoneri’s eighth European Cup will not come in 2025.

Yet 24 hours later, as part of a Milanese double bill against English opposition, came a contrasting display, of defiance in defence, sharpness on the break and tactical nous, to indicate Internazionale are their neighbours’ opposites as well as being their rivals. Pep Guardiola had argued they are a still better side than in the 2023 Champions League final, when they came agonisingly close to forcing extra time, at the least. Some of his compliments can seem exaggerated but this looked a realistic assessment as Inter held Manchester City and held their own against them. “We played better than we did in Istanbul,” Guardiola said.

There is other evidence to support his theory he faced more formidable opponents: Inter Milan finished 18 points off the pace in Serie A in 2022-23 and won it by 17 last season. If they can match City over 90 minutes, just maybe they could outperform them over nine months in Europe. Because if the top tier of favourites for the Champions League probably only consists of two teams – Real Madrid and City – there are reasons to place Inter prominently in the second bracket, containing possible winners.

Inter showed their substance at the Etihad Stadium. “We put in a giant performance,” said Simone Inzaghi. “I asked them to play exactly as they did. We all know what Manchester City are capable of. We knew we had to pull out all the stops and play a great game and we did it. We created some really good chances as well.”

Guardiola branded Inter “masters of defending”. The way Alessandro Bastoni patrolled Erling Haaland equips him to cope with anyone; the City manager argued Inter surrounded his striker with six players. It was Italian defending.

And the idiosyncrasies of Italian football means Inter represent a unique proposition. Serie A can feel an island; Inter fly in the face of other footballing fashions by playing 3-5-2, but it seemed to always give them players in space and they amassed 13 shots. “Italian teams are so difficult,” Guardiola said. “They create problems in transition.” Inter are neither anti-possession nor slaves to it but they were brilliantly configured.

Their nous is matched by their manager’s. Inzaghi can feel curiously undervalued outside his homeland but is one of the elite European managers. Winning the Champions League depends on a prowess in knockout ties and Inzaghi forged a reputation as a cup specialist, long before he won Serie A.

Yet now Serie A may represent a reason why Inter could be underestimated, if not by Guardiola. Its era of superiority is ever more distant: Inter’s 2010 Treble team were its last Champions League winners, though there is a broader pattern of an Italian renaissance in continental competitions.

Whereas it was once the league with the biggest budgets and names, now it is relatively shorn of stardust. Inter are challenging on the cheap, only in contention because of outstanding recruitment.

Piotr Zielinski, Marcus Thuram, Hakan Calhanoglu, Medhi Taremi and Henrikh Mkhitaryan were all free transfers, Francesco Acerbi, Yann Sommer, Yann Bisseck and Matteo Darmian were all acquired for under £10m. Since the 2023 final, they have survived the sales of Andre Onana and Marcelo Brozovic. They did not even own Romelu Lukaku then anyway.

City conquered Europe in part because they bought well, but with the luxury of more sizeable sums. If a team can win the Champions League with as many free transfers and cut-price recruits as Inter have, it would prompt the question of why hasn’t anyone else doesn’t do it. It renders it unlikely.

Yet there is quality and quantity. “They will be there for many years because they created a deep squad,” said Guardiola. The injured Federico DiMarco did not even travel to Manchester. Lautaro Martinez and Denzel Dumfries began on the bench but surely feature in Inzaghi’s best team; Davide Frattesi may do, too. Except that Inter already have a high-calibre midfield with high-profile admirers. “[Nicolo] Barella is an exceptional player and Calhanoglu,” said Guardiola. Zielinski, meanwhile, was exceptional when Napoli won Serie A. “We wanted Zielinski to join us because we knew he can give us a lot,” Inzaghi said.

There are options, too, and a manager of Inzaghi’s intelligence may perm the right ones. After the lost decade that followed Jose Mourinho’s 2010 triumph, Inter look on the up again. That picture could have been still clearer.

Last season’s Champions League represented a missed opportunity; they exited on penalties to Atletico Madrid when most of the favoured teams were on the other side of the draw. “This team won the Scudetto last season and didn’t do enough in the Champions League, so this year we want to do more in Europe,” Barella said. “We reached the final two years ago. Our ambition is to do it again, then in football anything can happen.”

Some have been more outlandish than Inter going one better than in 2023. Fifteen seasons since they last triumphed, with the European game arguably needing another winner, Inter have not been better equipped to challenge since Mourinho decamped for Madrid.