I didn't specifically notice the grimace before the tackle, bit the tackle itself did not look all that hard IMHO.
Well, he made a stupid tackle about 9 seconds after he came onto the field, but after that I thought it seemed like he settled down and played pretty decent. I didn't notice the grimace either (and I don't have it on my DVR anymore) but I also kind of thought that the tackle didn't look bad enough to injure him, even if his foot was already injured. Injuries are weird though, so who knows? Maybe he just got hit in exactly the wrong spot from exactly the wrong angle or something.
Dispatch article from today: http://www.dispatch.com/crew/crew.php?story=dispatch/2006/04/19/20060419-G3-01.html
I finally watched mine tonight and he certainly seems like he is hurt before the foul. He grimaces just as he plants his left foot.