McMillan (back) was spotted wearing a neck brace after Saturday's 17-14 preseason win at Pittsburgh, Rick Stroud of the Tampa Bay Times reports.
At the end of his 18-yard leaping catch in the first quarter, McMillan was undercut by a Steelers defender and landed hard on his neck and head region. He was able to walk to the sideline under his own power before being ruled out due to a back issue, while also being evaluated for a concussion. It's unclear if McMillan has been diagnosed with a head injury, but it seems likely that he'll miss some time with just one preseason game to go (Saturday, Aug. 23 against the Bills) ahead of Week 1.