Not seen that sort of blackening previously.

But please post a better focused image so we can see the detail clearly.

Let's see if this one is a little clearer

Sorry, I'm still puzzled.

How many leaves on the plant are affected?
If only that one, remove & discard.

If many more, please post image of entire plant.

I posted some pictures of leaves on one of my plants on another forum and Tomato Spotted Wilt Virus was mentioned. None of my leaves look as bad as the one in focus in your picture, but some of the leaves in the background of your picture look like mine. I also posted pictures on the Container Gardening forum and Growing Tomatoes forum on Gardenweb. Here's a link if you want to compare pictures.

http://forums2.gardenweb.com/forums/load/contain/msg072041346369.html?1

I found some thrips in my plant's blossoms and it's starting to resemble TSWV more and more each time I go out and inspect the plant. Maybe something to look into?