There's a trick from traditional darkroom work called "edge burn" where you subtly darken the edges around the photo radiating out from the primary subject. In PS this can be done with a multiply layer (opacity way down) and a radial gradient.
This mimics the way our eye sees things naturally, and provides a non-concious (I said 'subtle') focus.
You've basically already got the left side of that effect (maybe not so subtle) already.
You might also try duping the layer, adding a layer mask (reveal all), running USM, then applying a radial gradient to sharpen only the softer areas (grass) a bit.
There also seems to be a vertical line of lightness leading from his elbow to the bottom of the frame.
(hey, you asked)