Schar was named in coach Ottmar Hitzfeld's 23-man squad for the tournament, despite missing much of the club campaign after undergoing surgery on a problem to his patellar tendon in January.
The 22-year-old is now adamant that he is fully fit ahead of Switzerland's World Cup opener against Ecuador on Sunday.
"I am fit," said the Basel defender. "In preparation I did everything and I'm ready for the World Cup."
Schar is aware of the importance of getting off to a good start with a win over Ecuador in Brasilia.
And Schar has called on his team-mates to approach the Group E match as if it was a final.
"It will be a groundbreaking game," Schar added.
"We only have three group matches and need to tackle the first like a final."
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