Blatter missed giving a scheduled speech to open Thursday's session of FIFA's medical conference in a Zurich hotel.
FIFA chief medical officer Jiri Dvorak says Blatter has to "manage the situation," after the governing body was rocked Wednesday by an American federal racketeering case.
Blatter has stayed out of public view by avoiding three scheduled speech-making duties within 24 hours.
Two FIFA vice presidents were among seven men arrested Wednesday in a Zurich hotel.
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FIFA's headquarters in Zurich was also raided by Swiss federal agencies for a separate probe of the 2018-2022 World Cup bidding contests.
Blatter is scheduled to address FIFA's 209 member federations at 5 p.m. (1500 GMT).
