Thinking of switching up again...unload new Sigma 70-200?

Let me start by saying that the Sigma 70-200 f2.8 OS version is a spectacular lens for (almost) everything I need it for. Main problem is that I just don't find the AF fast enough for the sports I shoot. I've gotten some fantastic sports images from it, but the consistency is not good enough and it really seems to struggle with fast moving objects coming right at me. Unfortunately, my style tends to favor those kinds of images. For panning stuff, or any other use, I can honestly say that I find the Sigma to be VERY close in IQ to my (former) Canon MkII which is quite a compliment. Frankly, its one of the reasons I'm even struggling with the idea of a switch (again).

Initially, I am just thinking about trading the Sigma out for a couple of Canon primes, namely the 200mm f2.8 and 100 f2 or perhaps another 135 f2. I'd likely hang onto the 24-105 since its crazy sharp and unbelievably versatile. I have lots of experience with primes and tend to shoot at one focal length for sports so the primes don't concern me. What I am looking for is great IQ wide open at the long end.

Anyone think this is a reasonable idea or am I off my rocker to even think about this. My Sigma is only a few months old but I do feel like I've used it enough for sports to feel it might not be the panacea for having sold my Canon MkII that I'd hoped it would be.

Getting another Canon's 70-200/2.8II not an option? Sounds like you could/would enjoy the versatility of the zoom.

Julian, the zoom is nice and the MkII is the best, no question. My issue with the MkII repurchase is simply that I am not shooting many paid jobs any more due to family (a good thing!) so I don't really want to plunk down a lot of additional coin. Even selling the Sigma and the 24-105 would probably only net me about $2 which is just enough for the MkII but leave me with just that one lens.