Sorry.. lost the thread! (or my mind.. sometime I think that is the issue!) lol!
#1.. PLEASE quit shooting at F2.8!!!!!!! LOL! Try F8 for a while.. that will give you a wider DOF to work on this with.
#2.. PRACTICE.. and lots of it... and as you get better at keeping the focus where you want, start slowing going to wider apertures until you find a balance of APERTURE (DOF) / and FOCUS ACCURACY that works for you....
what I mean is this: I can shoot some moving objects all the time at F2.8, and get them sharp..... other moving objects, I need more DOF most of the time. There has to be a balance between skill, equipment, and settings... and you need to find that balance.
More skill can help and that will come with practice.
Better equipment (better, faster focusing, etc) can help.. and that can happen also.
In the meantime, set your settings to maximize your chances of getting the shots you want. Smaller aperture (Better DOF).. keep that shutter speed fast enough to catch the motion and STOP it (1/250 to 1/500.. the faster the better!). ISO set it to 400 on a bright sunny day, if you need to.. so you can optimize the other settings... or 800, etc...
shooting a small, near, fast moving object at F2.8 takes practice... and you will get there. In the meantime, work toward that... slowly.. walk before you run!
does that make sense? I have a bad migraine... and feel like I am rambling... lol!!
(as I said earlier.. try Aperture Priority for this.. set it to F8. Meter the scene.. and then set your ISO so that you get an average shutter speed of around 1/500 for that scene and lighting. Then SHOOT! have fun!)