The final rounds of the Champions League are often the finest exhibits of high-calibre football.

The first legs of the competition’s semi-finals provided compelling evidence of that last week, as Paris Saint-Germain edged Arsenal 1-0 at the Emirates Stadium, while Barcelona and Inter traded blows in a 3-3 draw in Catalonia.

With such fine margins in play, the smallest tweak in systems, pressing schemes or defensive organisation could provide tie-changing results. Here, The Athletic looks at five tactical trends that could determine who participates in the Champions League final in Munich on May 31.

PSG vs Arsenal

Can Arsenal find a way to stem PSG’s build-up play?

PSG’s fluidity was crucial to their third-minute goal scored by Ousmane Dembele in the first leg. Smooth positional interchanges between the front six, Achraf Hakimi’s positioning out wide and higher up the pitch, and crisp passing all bothered Arsenal in the opening 25 minutes.

Mikel Arteta’s solution was to instruct Martin Odegaard to lead Arsenal’s press instead of Leandro Trossard and push the Belgian wider while Gabriel Martinelli marked Hakimi.

In this example, that change led to Nuno Mendes — under pressure from Bukayo Saka and fearing Declan Rice might win the ball off Vitinha if he passed short — launching the ball out for a throw-in.

Arsenal’s in-possession play improved on the back of that change, but PSG found the counter-solution after the break. Centre-back Willian Pacho passes to Nuno Mendes under pressure from Odegaard. Saka moves up to press Mendes but is also watchful of Vitinha.

Saka closes down Mendes, with Fabian Ruiz now positioned out wide to pull Rice away from midfield. Mendes passes into the space Rice vacated for the retreating Dembele (not in frame).

William Saliba follows Dembele, with Trossard leaving Joao Neves to double up on the PSG striker. Dembele passes to Neves, who finds Hakimi.

In five seconds, PSG move the ball from their own box to the halfway line, taking seven Arsenal players out in the process.

Thomas Partey’s return and Dembele’s potential absence due to a hamstring injury bode well for Arsenal. But Bradley Barcola and Goncalo Ramos — who came on as substitutes for PSG in the first leg — are more than capable of leading the line. Both went close to scoring in the first leg through different moves — Barcola from a neat passing sequence and Ramos from Marquinhos’ ball over the top — illustrating the different approaches PSG can use in Dembele’s absence.

Will defensive set pieces be either team’s undoing?

For all of Arsenal’s prowess from offensive set pieces, they have struggled to defend them. They have conceded 26 chances from set plays in the Champions League this season, in addition to letting in goals from corners against Bournemouth and Palace in their last two Premier League matches. Marquinhos tested David Raya with a header from a later phase of a corner in the first leg, too.

PSG have not fared much better, conceding 28 chances from set pieces in Europe. Merino’s headed strike from a free kick was disallowed for offside in the first leg. Saka scored Arsenal’s opener from a direct free kick from the right wing when the teams met in the league phase back in October.

Corners and lateral free kicks could prove crucial on Wednesday.

Inter vs Barcelona

Can Inter stop Pedri from dictating play?

While Lamine Yamal rightfully dominated headlines after the first leg, Pedri’s display from midfield drove Barcelona.

The 22-year-old was afforded time on the ball with Inter dropping into a compact defensive shape focused on protecting their box and limiting Yamal. That meant Pedri often found himself in situations like the one below.

That allowed him to dictate proceedings. Pedri could cut Inter open in different ways. Here, he forms a triangle with Frenkie de Jong and Ferran Torres.

The trio exchange passes, with Torres feeding Pedri in behind the Inter defence. The midfielder turns back and passes to Yamal after pulling three defenders towards him. That frees Yamal up while giving Barcelona’s forwards space in the box.

The positional interchanges between Raphinha, Torres and Dani Olmo also allowed for line-breaking passes like the one below to the Brazilian.

Pedri was crucial to Barcelona’s second goal too, as he was given the time to pick out a pass over the top to Raphinha. The Brazilian squared for Torres to score.

Inter will hope to have more possession at home on Tuesday, which could marginally limit Pedri’s influence. But if they double or triple up on Yamal again, Pedri will have the space and time to make an impact again.

Can Inter use diagonal passes better to beat Barcelona’s offside trap?

Barcelona’s high line is difficult to bypass but not impossible. One way to beat the offside trap is by using diagonal balls that stretch the pitch. These are more effective than straight passes over the top or through-balls as they require defenders to shuffle across, during which the defensive line can become disjointed. That then creates space for the receiver of the pass to play in a more central player.

In the first leg, Inter attempted just three switches of play, of which only one reached its target. After Nicolo Barella and Hakan Calhanoglu overhit their switches in the first half, Mehdi Taremi — who replaced the injured Lautaro Martinez at half-time — found Denzel Dumfries, who covers some ground to reach it.

With Barcelona’s defensive line shifting over, Pau Cubarsi is caught in no man’s land while Inigo Martinez is unsure whether to push up or play the trap. Dumfries curves a pass to Marcus Thuram.

Wojciech Szczesny swept up before the offside flag was raised. Had Martinez dropped half a yard deeper or Thuram timed his run better, the Inter striker would have been in on goal or had teammates to pass to.

Diagonals are a viable solution for Barcelona’s high line but Inter have an alternative too…

Can Barcelona deal with Inter’s centre-back rotations?

A standout quality of Simone Inzaghi’s team is the seamless positional interchanges between their centre-backs and midfielders. They often progress the ball from the back by getting Henrikh Mkhitaryan or Calhanoglu (sometimes both) to become centre-backs, while their wide centre-backs move into midfield. This causes chaos for teams that press high or use man-marking schemes.

The other advantage it has is higher up the field. Twice against Barcelona, Inter’s wide centre-backs, Alessandro Bastoni on the left and Yann Bisseck on the right, moved near the opposition’s penalty area while the midfielders hung back

In the 11th minute, Bastoni receives a pass from Federico Dimarco in the box after running on the blindside of Yamal and Jules Kounde.

Bastoni delivers a deep cross, with the move eventually ending in Martinez, positioned offside, turning home Mkhitaryan’s shot from range.

The move worked in transitions, a dominant feature of Inter’s attack, given the limited possession they had.

In the 49th minute, Bisseck pushes up from centre-back to meet Dumfries’ pass in behind on Inigo Martinez’s blind side.

Bisseck’s cutback is deflected by Ronald Araujo to Dimarco, who skies his shot.

Barcelona could be without their first-choice full-backs for the second leg. Following Alejandro Balde’s left hamstring injury in April, Kounde was substituted in the 42nd minute of the first leg against Inter after injuring his left hamstring.

Inzaghi’s side could target the flanks through combinations between their wing-backs and wide centre-backs to catch Barcelona off guard.

(Top photos: Getty Images)