The 34-year-old scored all four goals in the 4-0 win over Sevilla on Thursday.
And Deschamps says Giroud always has to 'fight against everyone' to prove his worth.
"It's always important for attackers to score goals, whatever the match," he said at a press conference after Les Bleus were paired with Belgium in the Nations League semi-finals.
"But our analysis is done in relation to the opposition. When it's a Champions League match, against a Sevilla team that is very successful, it necessarily highlights Giroud's performance.
"He had the immense pleasure of being able to start a match. It does not happen to him often, even if by returning he scores important goals. Scoring a quadruple in the Champions League doesn't happen every day. Besides, they are different goals.
"Olivier is someone with a big mind, a big character. He is forced to fight against everyone, to excess at times. It was an important game as they played first place against Sevilla. Faced with such an opponent, it further enhances his performance. Good for him and for his club."
Deschamps added: "He was often decisive anyway in scoring or giving the last pass. He is a player who makes the differences.
"It's been a while since he scored in the Champions League but it happens. He wants to stop this series and be efficient, but that does not prevent him from doing decisive things for his club despite everything."