Blurred Frame Dall Sheep Ram, Denali National Park

The viewer's eye is drawn to contrast, which is lacking in a strongly blurred portion of the image. Thus, blurring the non-subject area aids in drawing the viewer's eye to the sharp-focused subject.

For this image, the telephoto compression and long distance beyond the subject create the background blur, and getting down into some close rocks takes the foreground out of focus, eliminating those distractions.

While I love the use of blur in photography, I rarely like foreground blur covering the subject's face.

A larger version of this image is available here.