Modric is in the middle of a protracted move to Real Madrid and Stimac, who took over from Slaven Bilic after the team's early Euro 2012 exit, said "time was running out" for the player ahead of the ties against Macedonia on September 7 and Belgium four days later.
"We can't carry the burden of his dilemma for him," Stimac told a news conference after including the Spurs playmaker in his squad.
"As the coach I will not allow the question of whether one particular player is fit to play or not to become the focus of attention ahead of two vital World Cup qualifiers."
Stimac, who came under fire from media and fans after a 4-2 defeat by Switzerland in last week's friendly in Split, has dropped left-back Danijel Pranjic and called up uncapped midfielder Josip Radosevic to his squad.
He also left out Dinamo Zagreb's Brazilian-born forward Sammir after including seven strikers in his squad.
"I would be delighted if Sammir was up to the national team's standards at this point in time but he is not," said the 44-year-old coach.
