Gutierrez is eligible to come off the 15-day disabled list as soon as he's ready, but he just took batting practice for the first time on Wednesday at Kauffman Stadium and the team remains unsure how soon he'll be able to begin a Minor League rehab stint.
"Sometimes when I wake up or am doing exercises or whatever, they come in different circumstances," he said. "I'm getting better every day, but until these go away I don't think I can do anything else. I hope they go away soon."
Gutierrez had already missed the first 63 games of this season due to a partially torn pectoral muscle, then sustained the concussion in his 13th game back.
Gutierrez said the 105-degree heat on Wednesday wasn't making things easier for his headaches, but he was drinking lots of fluids and doing everything he could to deal with the weather as well.
"He's been doing a lot of work and still has some things to do," manager Eric Wedge said. "He's feeling better, but still has some days that are better than others. So we don't have a firm plan to send him out just yet. And this heat doesn't help us much, to be honest."