En cada saque de esquina, la afición se pone nerviosa.

En cada means at/on each or in every in this kind of context.

In En cada saque de esquina, en is used to locate what happens during each corner kick:

• En cada partido = in every match
• En cada ocasión = on every occasion
• En cada saque de esquina = at every corner kick

Using a cada would sound wrong here. A is not the normal preposition for this time/situation meaning.

Saque de esquina is the standard Spanish term for a corner kick in football.

Breakdown:

• saque = a kick, throw, restart, taking of the ball into play
• de esquina = from the corner / corner-related

So literally it is something like corner restart or kick from the corner, but the natural English equivalent is corner kick.

In Spain, this is the normal football expression.

Because de esquina works like a fixed type/classification expression.

In Spanish, when one noun describes the type of another noun, the article is often omitted:

• sala de estar = living room
• zapatos de deporte = sports shoes
• saque de esquina = corner kick

If you said saque de la esquina, it would sound more literal, like a kick from the corner in a specific physical sense, not the standard football term.

Here, la afición means the fans, the supporters, or the crowd of supporters.

This is a very common sports meaning in Spain.

Although afición can also mean fondness, enthusiasm, or hobby interest in other contexts, in football language:

• la afición del Madrid
• la afición del Barça

means the club’s supporters/fanbase.

So in this sentence, la afición is a collective noun referring to the fans as a group.

Because afición is a collective singular noun.

It refers to many people, but grammatically it is treated as a singular feminine noun:

• la afición
• la afición se pone nerviosa

That is why both the verb and adjective are singular:

• se pone not se ponen
• nerviosa not nerviosos

English does this too sometimes with words like the crowd or the audience.

Because nerviosa agrees with la afición, which is:

• singular
• feminine

So:

• la afición → nerviosa

Even though the fans are many people, the grammatical subject is still the singular noun afición.

Compare:

• La afición está contenta.
• La gente se puso nerviosa.

Both afición and gente are singular feminine collective nouns.

Ponerse + adjective is a very common way to say to become or to get a certain emotional or physical state.

So:

• ponerse nervioso/a = to get nervous
• ponerse triste = to become sad
• ponerse contento/a = to become happy
• ponerse enfermo/a = to get ill

In the sentence:

• la afición se pone nerviosa

means the fans get nervous / the crowd becomes nervous.

This suggests a change of state: they are not necessarily nervous all the time, but they become nervous whenever there is a corner.

Here, se is part of the pronominal verb ponerse, which means to become or to get in many contexts.

Compare:

• poner = to put
• ponerse = to become / to put on / to get

Examples:

• Pone la mesa. = He/She sets the table.
• Se pone nerviosa. = He/She gets nervous.
• Se pone el abrigo. = He/She puts on the coat.

So in your sentence, se pone nerviosa is not literally puts herself nervous. It is just the normal Spanish structure for gets nervous.

Yes, but the meaning changes slightly.

• se pone nerviosa = gets nervous, becomes nervous
• está nerviosa = is nervous

In this sentence, se pone nerviosa is better because it shows the fans’ reaction each time a corner happens.

Compare:

• En cada saque de esquina, la afición se pone nerviosa.
  = At every corner kick, the fans get nervous.
• En cada saque de esquina, la afición está nerviosa.
  = At every corner kick, the fans are nervous.

The second one is possible, but the first is more dynamic and feels more natural as a repeated reaction.

The comma separates the opening time/context phrase from the main clause:

• En cada saque de esquina, = context/frame
• la afición se pone nerviosa. = main statement

This comma is very natural in Spanish when a sentence begins with a longer introductory phrase. It helps readability.

It is not always absolutely required in every short sentence, but here it is standard and clear.

They are very close in meaning.

• En cada saque de esquina = at every corner kick
• Cada vez que hay un saque de esquina = every time there is a corner kick

The first is more compact and idiomatic in sports writing or commentary.
The second is more explicit and slightly longer.

Both are correct:

• En cada saque de esquina, la afición se pone nerviosa.
• Cada vez que hay un saque de esquina, la afición se pone nerviosa.

Yes, very often.

In Spain, la afición is a very common sports word for the supporters as a group. You will hear it in:

• commentary
• sports journalism
• interviews
• everyday football talk

For example:

• La afición apoyó al equipo hasta el final.
• La afición estaba entregada.
• La afición se impacientó.

So this sentence sounds natural and very Spanish, especially in a football context.

Yes. Because la afición is a collective noun, possible natural translations include:

• the fans
• the supporters
• the crowd

The best choice depends on context:

• the fans/supporters focuses on the people as followers of the team
• the crowd focuses more on the stadium atmosphere

So The crowd gets nervous at every corner is a perfectly reasonable translation in context, even if the Spanish word is literally closer to the supporters/fanbase.