Jucătorul alege perechea de dublu.

In Romanian, the definite article is usually attached to the end of the noun instead of being a separate word like the in English.

So:

• jucător = player
• jucătorul = the player

The ending -ul is the masculine singular definite article here.

For the same reason: it is the definite form of the noun.

• pereche = pair
• perechea = the pair

Because pereche is feminine, the definite article appears here as -a.

So both main nouns in the sentence are definite:

• jucătorul = the player
• perechea = the pair

Alege is the 3rd person singular present tense form of the verb a alege, meaning to choose.

That matches the subject jucătorul = the player, which is third person singular.

A few present-tense forms are:

• eu aleg = I choose
• tu alegi = you choose
• el/ea alege = he/she chooses

So Jucătorul alege means The player chooses.

De dublu means something like for doubles or used in doubles.

In sports contexts, dublu refers to the doubles event or doubles play. So:

• pereche de dublu = doubles pair / pair for doubles

This is a very natural Romanian way to express that the pair is the one used in the doubles event.

Because dublu is being used in a general, category-type expression after de.

Romanian often uses this structure:

• X de Y = X of Y / X for Y / X related to Y

Here, dublu names the type of event, not a specific individual thing. So de dublu means for doubles in a general sense, not of the doubles.

Yes, perechea de dublu is the direct object of alege.

Romanian does have cases, but for many nouns the nominative and accusative forms are identical. That is what happens here.

So:

• subject: Jucătorul
• verb: alege
• direct object: perechea de dublu

There is no special extra marking on perechea just because it is the direct object.

Romanian often uses pe before direct objects that are people or otherwise strongly specific/animate.

Examples:

• Văd pe profesor. = I see the teacher.
• Îl caut pe Andrei. = I am looking for Andrei.

But perechea is not a person here, so pe is not used.

That is why the sentence is simply:

• Jucătorul alege perechea de dublu.

not

• Jucătorul alege pe perechea de dublu.

Yes. This is the most neutral Romanian word order:

• Subject + Verb + Object
• Jucătorul alege perechea de dublu.

Romanian word order is somewhat flexible, but changing it usually changes the emphasis.

For example, you could front the object for emphasis, but then Romanian often adds a clitic:

• Perechea de dublu o alege jucătorul.

That sounds more like It is the doubles pair that the player chooses.

So the original sentence is the most straightforward, standard version.

Then the subject noun would change to the feminine form:

• jucătoare = female player
• jucătoarea = the female player

So the sentence becomes:

• Jucătoarea alege perechea de dublu.

The verb alege stays the same, because it is still third person singular.

The letter ă is a very common Romanian vowel. It is a short, neutral sound, somewhat like the a in English about, though not exactly the same in every accent comparison.

So jucătorul is pronounced approximately like:

• joo-kuh-TOR-ul

Very roughly:

• ju = like joo
• că = a short neutral kuh
• to = stressed syllable here
• rul = final rul

The stress is on țo in jucătorul:

• ju-că-TO-rul

Sometimes yes, depending on context, but they are not always identical.

• pereche = pair
• echipă = team

In doubles sports, pereche is often especially natural when you mean the two players considered together as a pair. Echipă is broader and can sound more like team.

So perechea de dublu is a very good, natural choice when talking about a doubles pairing.