Modric was left out of manager Igor Stimac's squad in August due to the ongoing transfer saga involving the midfielder.
However, Modric has since secured a £33m move to Madrid, playing twice for the Spanish giants already, and he believes that he is ready to play the whole match.
"I am very happy and in good physical shape," he told index.hr.
"Now I am ready to play for 90 minutes but the coach will have to decide how much time I will have out there."
Croatia will face Macedonia tomorrow before going on to play Belgium on September 11.