La defensa volvió al banquillo por la lesión y bebió agua despacio.

Because volvió and bebió are in the preterite (pretérito indefinido), which is commonly used for completed actions in a story.

Here, the sentence tells us about two finished actions:

• she/the defender returned to the bench
• she/the defender drank water

If you used volvía and bebía instead, that would suggest an ongoing background action, repeated action, or a descriptive scene rather than a simple sequence of completed events.

So this sentence sounds like a straightforward match report or narration:

• volvió = came back / returned
• bebió = drank

The accent mark shows the correct stress: vol-VIÓ.

It also helps distinguish the past form volvió from other forms of volver. In writing, many Spanish past-tense forms in the third person singular end in -ó, and that final vowel is written with an accent:

• volvió
• bebió
• corrió
• salió

So the accent is a normal spelling feature of that verb form.

Al is the contraction of a + el.

So:

• a el banquillo → al banquillo

Spanish always contracts a el to al, except when el is part of a proper name.

Examples:

• Voy al estadio.
• Regresó al hotel.

So volvió al banquillo literally has to the bench.

Because por expresses the cause or reason here.

• por la lesión = because of the injury

That is exactly the idea in this sentence: the return to the bench happened due to the injury.

By contrast, para usually expresses things like:

• purpose
• destination
• deadline
• intended recipient

So para la lesión would not fit this meaning.

A useful shortcut:

• por = because of / due to
• para = for / in order to / intended for

In this sentence, banquillo means the bench in a sports context, especially the substitutes’ or sidelines bench.

In Spain, banquillo is a very common sports word. It can also appear in other meanings in different contexts, such as the dock in a courtroom, but here the sports meaning is the natural one.

So volver al banquillo means something like:

• return to the bench
• go back to the bench

Yes, defensa can mean defense, but in sports it can also mean a defender.

That creates a possible ambiguity:

• la defensa = the defense line / defense
• la defensa = the female defender

In real context, the rest of the sentence usually tells you which meaning is intended. Since this sentence says volvió al banquillo and bebió agua despacio, it sounds very natural to understand it as referring to a player, especially a female defender.

A useful note:

• el defensa = the male defender
• la defensa = the female defender

So even though the noun ends in -a, it can refer to either a male or female player depending on the article.

Because agua is being used in a general, uncountable sense: she drank water, not a specific water.

In Spanish, with uncountable nouns after verbs like beber, it is very common to leave out the article:

• bebió agua
• compró pan
• necesito dinero

If you added an article, it would sound more specific:

• bebió el agua = she drank the water

That would mean some particular water already known in the context.

Both can mean slowly, but despacio is often more common and natural in everyday speech.

• despacio = slowly, at a slow pace
• lentamente = slowly, more formal or stylistically heavier in many contexts

So bebió agua despacio sounds very natural and conversational.

You will hear despacio a lot in Spain:

• Habla despacio.
• Camina despacio.

Because Spanish often omits subject pronouns and repeated subjects when they are already clear from the verb forms and context.

Here, the subject of volvió and bebió is understood to be the same:

• La defensa volvió al banquillo por la lesión y bebió agua despacio.

Spanish does this very naturally. Repeating the subject would usually sound unnecessary unless you wanted emphasis or contrast.

For example, this is possible but less natural in a neutral sentence:

• La defensa volvió al banquillo por la lesión y la defensa bebió agua despacio.

Yes. Spanish word order is more flexible than English word order, although the version in the sentence is the most neutral and natural.

For example, you could also say:

• La defensa volvió al banquillo por la lesión y despacio bebió agua.
• La defensa, por la lesión, volvió al banquillo y bebió agua despacio.

But these alternatives may sound more literary, marked, or focused in a different way.

The original order is the most straightforward:

• subject
• verb
• place/result
• reason
• second verb
• object
• adverb

So it works well as a normal narrative sentence.

When volver means to return to a place, it is normally followed by a:

• volver al banquillo
• volver a casa
• volver al vestuario

Be careful, though: volver a + infinitive is a different structure meaning to do something again:

• volvió a jugar = she played again
• volvió a beber agua = she drank water again

So:

• volver a + place = return to a place
• volver a + infinitive = do something again

That is a very common point for learners.