The things I like are that you captured the animal in a good pose, exhibiting natural behavior in the wild. He's surrounded by leaves and grass which act as good compositional elements.
Unfortunately, your subject is not in focus. You can see the blades of grass just behind the squirrel in focus. In my opinion, there's no amount of post production that will save this. In the future, pay close attention to your focus point, and if necessary and if possible, use a slightly smaller aperture to give you a bit more margin of error.
If it had been sharp, I would still knock a few aspects. #1, the subject of the photo is dead center. While this is not always automatically bad, it leaves for a very uninteresting composition in this photo, at this distance, with this focal length. Tighter framing when shooting would have also eliminated some distracting elements in the background, such as the big tree and the children playing. Both are very distracting, as one is a black hole, and the other introduces punches of color in an otherwise monotone-ish scene. Also, the path in the background, which is visible just above the squirrel's head is near to creating a tangent with the tip of the ear.
