Training smaller muscle groups is truly crucial for any athlete, or really anyone who wants power in their movements. Whatever strength you have is only temporary and underdeveloped if you don't train your stabilizing muscles. The way that most people work out isn't too good in terms of building muscle in those stabilizers, and thus minimizes athletic strength and power.
Let's break it down, I'll use the bicep curl as an example. Doing a bicep curl requires that you take the weight and curl it til it almost touches your shoulder, and then bring it back down for a full range of motion. But what does a full range of motion really mean? Your muscle isn't nearly as taxed at the top of the curl as it is at the bottom.
Furthermore, training such straight line movements is unrealistic for athletic application, when you'll be twisting, bending, and working your arms, legs, spine, and whole body in angles that you can't reach by training in a straight line. You won't train those smaller muscle groups as well with those exercises. Full range of motion doesn't always mean full strength transfer.
So sometimes, if you're doing conventional lifting, you'll need to sit down with a dumbbell and try to work every possible angle that your limb could move in. Training big, compound movements will help with this a lot as well.
OR, you could train in an unconventional, or odd, way by lifting odd objects. Do you have the strength to curl a 50lb dumbbell? If so, that's pretty solid! Try working out with a 50 lb kettlebell, however, and your workout's intensity will completely change. The kettlebell's grip and odd distribution of weight makes it much more difficult to handle than most dumbbells. Another great, odd object to lift is the Atlas stone. Picking up a large, heavy, spherical stone with NO HANDLES is truly intense for your whole body. You've got to get into a squat to lift it, then work your back to support it, and essentially bear hug the dang thing, employing chest, forearms, lats, and all manner of stabilizing muscles in ways that you couldn't work them with conventional lifting. Your level of athletic strength and power will skyrocket because the way those workouts will train your smaller muscles will surpass the average workout for someone training large muscle groups.
Bodyweight training is also a great way to strengthen the underdeveloped, stabilizing muscles. You may be proud of your strength in the back row, but trying to perform a full front lever will add some extra difficulty. It'll activate your core, your shoulders, and your forearms in addition to those lovely back muscles you train in the row.
For me, the bodyweight exercise that's really kicking my butt and training my smaller muscles is the planche. My core is increasing in thickness from my sides to my lower back. My shoulders are bulging with added power. My upper chest muscles that aren't often trained get a hard workout from planche training.
Getting the kind of power you want, as well as the physique with well-distributed muscle you'd want, will require you to really put some focus on those stabilizing muscles. Your true athletic strength and power will then show.