For most sports use we would now recommend an autofocus binocular as they neatly side step the need for constant re-focusing as the action moves to and fro. You also don't want too much magnification or you'll be viewing individual horses instead of the pack (or viewing a player instead of the action going on around him)!
For most sports use a 7x 35 autofocus binocular is a good mix of optical characteristics and practical size so you can easily carry it around or fit in your pack.
Note that with autofocus binoculars everything is focused from about 20 yards or so onwards (it depends on the make and model). You won't be able to use them for close up observation nor will you be able to use them if you have significant imbalance of vision between your eyes as they assume one has balanced eyesight. You don't need to be 20/20 just reasonably well balanced.