Weird and wonderful things are happening at Barcelona this season. Their games have brought more goals than any other team in Europe’s top five leagues. They have trapped more opponents offside than any club, too. Their kamikaze high line gives matches a bizarre look and similarly bizarre things seem to unfold: last week goalkeeper Wojciech Szczesny impaled his own defender with his kneecap; in the same game, captain Raphinha scored from outside the box with his face.

All of which might be worthy of mockery if it wasn’t quite so effective, like Tottenham but with points. Barcelona are second in the Champions League table behind Liverpool, the only two clubs to have already qualified for the last 16 before Wednesday night’s grand finale. They are third in La Liga and still in the title race after a recent dip in results.

Robert Lewandowski is still brilliant at 36, leading the scoring charts in La Liga and the Champions League. Raphinha has turned into one of the best players in the world. Pedri’s passing stats fall off the edge of every graph and Lamine Yamal continues his ascension towards footballing greatness.

The manager, Hansi Flick, has built a highly entertaining yet fallible team, and perhaps the most fascinating thing about this incarnation of Barcelona is that no other major team in Europe plays the game quite like they do. The goalkeeper sweeps half the pitch, the defence take up station on the halfway line while midfielders and forwards press as if their lives depend on it, smothering opposition to force mistakes. They average 67 per cent possession and their opponents’ average pass-completion rate is the lowest among Europe’s top five leagues.

At the heart of Flick’s plan is a commitment to an offside trap bordering on cultish lunacy. The most offsides accumulated by any defence in the Premier League is Brighton with 65, and in the Bundesliga it’s Stuttgart with 54. Barcelona have provoked 115 offsides in La Liga this season, with a drilled defence that leave 50-yard spaces behind them. “It looks dangerous, but it’s not dangerous,” Flick insists.

The 59-year-old has always adopted a front-foot style and it brought great success at Bayern Munich, but this is something altogether more experimental. When it works, as it did in October’s Clasico win over Real Madrid when Barca’s defence caught Kylian Mbappe offside eight times in 30 minutes, it can make strikers look foolish. Flick’s methods require utter devotion and commitment to the grift. “Anyone who drops back by one metre,” he told his players at half-time at the Bernabeu, “I’ll substitute them.”

It is one of the starkest evolutions of the game in the VAR era, a high-risk ploy made possible by La Liga’s semi-automated offside technology which sniffs out the most minor infringement. Some of Madrid’s offsides came down to inches but that was not luck: seconds before Mbappe thought he’d scored, replays showed how Barca’s 18-year-old centre-back Pau Cubarsi checked his run for just a moment, enough time for the striker to run half a torso too far.

One problem, Flick has complained, is that assistant referees rarely raise their flag for close calls, and it means his defenders spend energy chasing back before the flag eventually goes up.

But he has another challenge, which is that opponents are increasingly plotting inventive ways to pierce Barcelona’s high line, which has proved susceptible to two attacks in particular. The first is what Real Sociedad striker Take Kubo called “secondary runs from midfield”, as he explained after their win over Barcelona in November. “We worked on their high line,” he told ESPN. “I am not sure they take into account the runs from the second line, the midfielders, even the defensive midfielder … I think those situations are difficult for them because they stop the line watching the striker or the wide men.”

The second is the run of a wide player in behind Barca’s full-backs, especially on the counter-attack. Flick commits men forwards with reckless abandon and immediately after possession turns over there is often space behind right-back Jules Kounde and left-back Alex Balde to exploit. In December’s key defeat by title rivals Atletico Madrid, Alexander Sorloth’s winner came after right-back Nahuel Molina surged into space down the wing before crossing into the centre. Osasuna and Las Palmas both earned league wins over Barcelona with goals scored from the space a full-back had vacated.

A recent run of only one league win in seven games brought scrutiny of Flick’s tactics. When Barcelona give up chances they are often one-on-ones – the average xG per shot against their goal of 0.13 is the highest in La Liga. But the manager rejects the idea that Barcelona had been “found out”, suggesting that his tiring midfielders are unable to press at the rate they produced earlier in the season. A 7-1 thrashing of Valencia at the weekend has eased some of those concerns, for now.

This has tended to be the way this season: teams either break through Barca’s pressing wall or get crushed. Ultimate judgement on Flick’s tactical experiment will come in their trophy count, and whether his offside trap is mimicked by the wider game may depend on whether he can make it work on a stage like the Champions League final. What is undeniable is that Barca are the most entertaining team in Europe right now, playing a brand of end-to-end football that flies in the face of convention.

Modern football faces increasingly loud accusations of being one homogeneous tactical recipe, a bland soup created in a laboratory by Pep Guardiola and followed to the ounce by every aspiring young coach. But at the club where Guardiola made his name, an old manager might be reinventing how football looks all over again.