Perfect Modals

We use must + have + past participle to express certainty about the past.

What do you think is a certainty in the past of Messi?

He must have trained hard when he was younger.

We use might/may/could + have + past participle to express possibilities in the past.

What do you think happened?

It might have been an accident.

It may have been a terrorist attack.

It could have been a performace.

We use can't/couldn't + have + past participle to express impossibility of a situation in the past.

We use should/ought to + have + past participle to express regrets or criticism of past actions.

You shouldn't have left the dog in the car.

You ought to have been more responsible.

We use could have + past participle to express suggested alternatives to past actions.

- Nadal won the match, but it could have won Federer.

We use needn't have + past participle to express something that happened in the past, but it wasn't necessary.

- It was an informal party, she needn't have worn such an elegant dress.

What's the logical explanation?

What's another possibility?

Make your own hyphotesis.