Hazard also missed Belgium's 4-2 win over the United States in Cleveland last week but has been in full training ahead of the Serbia match in Brussels.
"I have done everything to get fit but I won't be at 100 percent. I'm not yet pain free, there is still some irritation," he told a news conference in Genk on Thursday.
Hazard was injured against Aston Villa in early May and missed the final win over Benfica in Amsterdam.
"I will not take any unnecessary risks. The match against Serbia is important but to be fit for the start of pre-season training at Chelsea is also," he said.
"The last thing I want is to return from holiday with an injury. If I don't feel I'm ready to play I will be honest with the national team coach," he said.
Belgian papers reported that manager Marc Wilmots might use Hazard as an impact player off the bench.
"That is an option but it's the coach's choice," the midfielder said.
"There is a good chance that a decision on my availability will only be made on field during the warm-up. This is the first time I've been side-lined this long with an injury but that is part of a football career."
Hazard was also asked about the arrival of Jose Mourinho as the new Chelsea manager.
"I'll be a little intimidated at the first training but in the end Mourinho is human like the rest of us," he said. "He has come to win trophies and that's my ambition too."