For sports, high performance autofocus can be really beneficial in a camera. If you're going to consider a used 70D, you also might consider a used 7D. On the surface, their 19-point AF systems appear similar. But the 7D's is actually a bit faster and better tracking fast moving subjects. The reason for this is that the 7D uses a separate chip to run the AF, similar to what Canon 1D-series cameras do (as well as dual processors to handle images). The 70D uses a single processor to handle everything.
Both cameras have all "cross type" AF points, like the 9-point system in your 700D (Rebel T5i in N. America).
The 70D has three AF patterns: All Points/Auto Selection and Single Point/Manual Selection (like all Canon cameras), plus Zone Focus, which is sort of like a scaled down All Points. The 7D has five patterns... the same three as 70D plus Expansion Points (you select the starting point, but the camera can expand to use surrounding poiints if needed) and Spot Focus (a high precision Single Point using a smaller than usual AF point, great for some things, but slightly slower than Single Point).
The 70D is slightly higher resolution (about 20MP), but a little slower at around 6 frames per second. 7D is 18MP and can shoot at up to 8 fps (though it does slow a bit for AF and metering at times).
Both cameras are better built than your 700D/T5i. The 7D especially is more robust, rated for up to 150,000 actuations. (70D is probably 100,000, while 700D is probably 75,000.) Both cameras also have 1/8000 top shutter speed and 1/250 flash sync (compared to 700D's 1/4000 and 1/200). In it's day (introduced around 2009), the 7D was the top of the line sports/action camera short of a 1D-series model.
The Rebel/xxxD series also all use a "penta-mirror" to reduce cost and weight. Both 70D and 7D use true pentaprisms which make for a bit bigger and brighter viewfinder (slightly offset by the Active Matrix focusing screen they use, which reduces viewfinder brightness slightly). I should note that a lot of people who have never used the new, Active Matrix focusing screens often find them a little difficult at first. But, once learned they work great.
Your 700d probably had a 95% coverage viewfinder. The 70D has 97 or 98%. The 7D's is 100%.... WYSIWYG.
7D use Compact Flash memory cards. 70D use SD cards.
They both use the larger LP-E6/E6N batteries, which are good for approx. 2X as many shots as the Rebel/xxxD cameras with their much smaller batteries (LP-E8 and now LP-E17).
Both 70D and 7D use a bit different control and display layout than 700D/T5i. There's more direct access to some functions, making for faster handling. The 7D, in particular, can be pretty easily and quickly adjusted without having to move the camera away from your eye.
70D has a rear LCD monitor that's articulated like your 700D's... but the 70D's is a Touchscreen. It also was the first Canon DSLR to use Dual Pixel Auto Focus in Live View. DPAF is significantly faster than earlier contrast detection AF method used in Live View on earlier models like yours. 7D (and 7DII) LCD screen is not articulated, nor is it a Touchscreen.
Other, later cameras use similar AF or sensors... T6i/750D and T6s/760D introduced a new 24MP sensor, but both use 19-point AF very similar to 70D's.
7D Mark II uses a 20MP sensor similar to 70D's (but now able to shoot at 10 fps), but has a unique 65-point AF system (now with 7 focus patterns). 80D inherited the 24MP sensor from the T6i/T6s, but introduced a new 45-point AF system (with five focus patterns). Perhaps most significantly, these AF systems also are -3EV rated, able to focus in two or more stops lower light than most of the previous models... and are at least partially "f/8 capable", meaning they can autofocus more lens/teleconverter combinations than earlier cameras.
The T7i/800D and 77D/9000D are essentially upgrades of the T6i and T6s, same 24MP, but now using the same 45-point AF system as the 80D (which is now also being used in the new 6D Mark II full frame model).
I shot sports with a pair of 7D for five years before upgrading to a pair of 7D Mark II almost two years ago. One minor thing with 7D is that they were the first model to use a then-new 18MP sensor and Canon fitted them with too strong anti-aliasing filters. So their images are fine and have very good detail, but need more sharpening than most of the earlier and later models. Canon also issues a white paper at the time they introduced the 7D recommending using slightly higher shutter speeds because the high density image sensors were a bit more susceptible to camera shake blur. Since sensors have only become more densely crowded in subsequent models, this continues to be true. With my cameras I tend to use ISO 400 as my lowest setting (lower ISOs don't really show much image quality improvement anyway).
For really fast action/sports shooting, pair up a 7D-series model or 70D/80D with a high performance USM lens. The EF 70-200mm f/4 is excellent... the bigger, heavier, more expensive f/2.8 versions are even faster focusing. For general purpose, the STM lenses are fine... though a bit slower focusing. STM are quieter/smoother, so are preferred for video. An exception is the fairly new EF-S 18-135mm IS USM... which uses a new "Nano" USM focus drive that's the best of both worlds. It's fast like USM, as well as quiet/smooth like STM. To date, Canon is only using the new Nano USM on three lenses (the others are EF 24-105L f/4L IS USM "II" and EF 70-300mm IS USM "II").
Yes, you can use slower cameras and lenses with a pre-focus, then wait technique... Sometimes it works (we used it a lot back in the days of manual focus). But it's pretty limiting, can be difficult in some cases (such as when using large apertures with shallow depth of field) and doesn't work at all in quite a few situations (such as when you can't predict the path a moving subject will take). A camera/lens combo with high performance AF will simply give you more options when shooting sports. Same with Image Stabilization. A lot of folks will tell you it's not needed with sports photography, because you'll be using high shutter speeds anyway... But IMO that's not true. I've been using various lenses with it for over fifteen years now and IS is especially useful on telephotos, generally makes for better shots and allows some techniques that would be difficult or impossible without it... even when shooting sports.
Hope this helps!