Thủ môn nhìn cầu thủ.

It uses the very common Vietnamese pattern Subject + Verb + Object:

• Thủ môn = subject
• nhìn = verb
• cầu thủ = object

So the structure is straightforward: The goalkeeper looks at the player.

Vietnamese often leaves nouns bare, without articles.

So thủ môn can mean the goalkeeper or a goalkeeper, and cầu thủ can mean the player or a player. Context usually tells you which meaning is intended.

If you want to make something clearly indefinite, you can add một:

• Một thủ môn nhìn một cầu thủ = A goalkeeper looks at a player

Vietnamese also does not need a classifier in a simple bare-noun sentence like this.

You usually do not know tense from the verb form alone, because Vietnamese verbs do not conjugate like English verbs.

nhìn can mean something like looks, is looking, or sometimes looked, depending on context.

If you want to be more explicit, Vietnamese often adds time words or aspect markers:

• đang nhìn = is looking
• đã nhìn = looked / has looked
• sẽ nhìn = will look

So Thủ môn nhìn cầu thủ is tense-neutral by itself.

Because Vietnamese nhìn can take its object directly.

English says look at someone, but Vietnamese usually just says nhìn ai.

So:

• nhìn cầu thủ = look at the player

You do not need a separate preposition here.

By itself, cầu thủ does not clearly show singular or plural. Vietnamese often leaves that to context.

So in different situations, it could mean:

• the player
• a player
• sometimes even players

If you want to make plural clear, you can add words like:

• các cầu thủ = the players
• những cầu thủ = players / some players

The same is true for thủ môn as well.

• thủ môn = goalkeeper
• cầu thủ = player, often especially a football/soccer player

Because thủ môn is a sports role, this sentence strongly suggests a football/soccer context. So cầu thủ here is most naturally understood as player in that same context.

Not exactly.

• nhìn = look at
• xem = watch, look at, check, depending on context
• thấy = see, notice

So in this sentence, nhìn is a good match for look at.

Compare:

• Thủ môn nhìn cầu thủ = The goalkeeper looks at the player
• Thủ môn thấy cầu thủ = The goalkeeper sees the player
• Thủ môn xem trận đấu = The goalkeeper watches the match

The tones are important:

• thủ = hỏi tone
• môn = level tone
• nhìn = huyền tone
• cầu = huyền tone
• thủ = hỏi tone again

A few sound notes:

• nh in nhìn sounds roughly like ny in canyon
• th in Vietnamese is not the English th in think; it is closer to an aspirated t
• the tones matter just as much as the consonants and vowels

So the biggest pronunciation challenge is usually getting both the sounds and the tones right, especially in thủ and nhìn.