Llamaré mañana en cualquier caso.

Both are correct, but they are slightly different in style.

• Llamaré is the simple future of llamar and means I will call.
• Voy a llamar is the near future structure and also means I’m going to call.

In everyday spoken Spanish, voy a llamar is often very common, but llamaré is also completely natural. In this sentence, llamaré sounds a little more definite or firm.

Llamaré is:

• first person singular: I
• future tense
• from the verb llamar: to call

The future endings are added to the infinitive:

• llamaré = I will call
• llamarás = you will call
• llamará = he/she will call
• llamaremos = we will call
• llamaréis = you all will call
• llamarán = they will call

Spanish often leaves out subject pronouns because the verb ending already shows who is doing the action.

• Llamaré already means I will call
• so yo llamaré is usually unnecessary

You can include yo for emphasis or contrast, but normally it is omitted.

Here, mañana means tomorrow.

Spanish mañana can mean:

• morning
• tomorrow

The context tells you which one is intended. In Llamaré mañana, it almost always means I will call tomorrow, because that fits naturally with the future tense.

If you wanted to clearly say in the morning, you would often say something like:

• Llamaré por la mañana = I’ll call in the morning

Yes, en cualquier caso is a common fixed expression. It means:

• in any case
• anyway
• at any rate

It is used to show that something will happen regardless of other circumstances.

So the sentence suggests:

• whatever happens,
• or regardless of previous discussion,
• I’ll call tomorrow anyway / in any case.

Yes. Spanish word order is flexible, especially with adverbial expressions like this one.

All of these are possible:

• Llamaré mañana en cualquier caso.
• En cualquier caso, llamaré mañana.
• Mañana llamaré en cualquier caso.

They all mean roughly the same thing, but the focus changes slightly.

• En cualquier caso at the start gives that idea more prominence.
• The original version sounds natural and balanced.

Yes. In Spain, llamar is the normal verb for to call someone, especially on the phone.

Examples:

• Te llamo luego. = I’ll call you later.
• Me llamó ayer. = He/She called me yesterday.

If you want to make the phone idea extra explicit, you can also say:

• llamar por teléfono

But usually llamar by itself is enough.

Yes, absolutely. That would mean I’ll call you tomorrow in any case.

The original sentence leaves out the person being called. Spanish often omits the object if it is already understood from context.

So:

• Llamaré mañana en cualquier caso. = I’ll call tomorrow in any case.
• Te llamaré mañana en cualquier caso. = I’ll call you tomorrow in any case.

That is because idiomatic expressions often do not match English word for word.

Literally, en cualquier caso is something like in any case:

• en = in
• cualquier = any
• caso = case

But you should learn it as a whole phrase, not by trying to build the meaning from each word every time. Spanish uses many expressions like this where the natural translation is more important than the literal one.

They are related, but used differently.

• cualquier comes before a singular noun:
  • cualquier caso = any case
• cualquiera usually stands alone or comes after the noun:
  • uno cualquiera = any one / just any one
  • cualquiera puede hacerlo = anyone can do it

In this sentence, caso is a noun, so cualquier is the correct form.

It is neutral. Nothing in the sentence is especially formal or especially informal.

• Llamaré mañana en cualquier caso could be said in normal conversation.
• It could also appear in writing or in a more formal context.

If anything, en cualquier caso can sound slightly more polished than simply de todas formas or de todos modos, but it is still very natural.