Idiom
second-guess someonesecond-guess (someone/something)
1.
to try to guess what will happen or what someone will do.
It's not for us to second-guess the court's decision - we'll just have to wait and see.
2.
(American & Australian) to criticize someone's actions or an event after it has happened.
It's easy to second-guess the team's coach - but let's face it, he made big mistakes.