Doubtless you’ve had to explain many times to beginners that they should be cutting at an angle rather than straight towards the sideline. Perhaps you’ve thought of a really good reason why – but just in case you haven’t, here’s my take on it.
It’s not anything to do with the angle of the cut relative to the throw – it couldn’t be, because a sideways cut when the disc is on the sideline is the same relative angle as a 45° in-cut with the disc in the centre of the field (imagining a vertical stack in this example). Some angles are easy to throw to and some are less so, but it’s certainly not the case that a sideways cut always produces the most difficult angle.
So it must be to do with the angle of the cut relative to the pitch itself. Which means it must be to do with the shape of the pitch; the available space. Here’s how.
Wherever you are on the pitch (outside the endzones), the shortest distance to an out-of-bounds line is ALWAYS directly sideways. [If you’re outside the endzone, you’re at least 18m from the end of the pitch – or 23m under USAU rules – and you can never be more than 18.5m from the nearest sideline.]
So, more relevantly, the direction in which the thrower will have least time to hit you before you run out of road is ALWAYS directly sideways. Cutting in any other direction gives your thrower more time. It gives them options. They can throw early, or they can fake to make space and you’ll still be a viable receiver. Maybe they’re looking elsewhere when you start the cut, but they’ll still have time to see you and make the throw.
(N.B. – even if you’re cutting to the far sideline rather than the near one, you’ll still get even more time if you angle the cut. It may be that a flat cut to the far side actually has more space than an angled cut to the near side but, given a prior choice of cutting to the open or break side, you’ll always get more time by angling the cut.)
As an aside, why don’t we always cut at really steep angles, giving ourselves yet more time? Well, we often do, on deep cuts; but on in-cuts our secondary intention – to gain the most possible yards – means we can apply a similar argument to the one above. Cutting straight back down the field is the fastest way to reduce the yardage gain if the pass is delayed at all. A 45° in-cut ‘loses’ yardage 40% slower than running straight back down the field (and – also importantly – changes the point of attack).
This balance – steep cuts eat up yards, but flat cuts run out of space – is (part of*) the reason why many teams will angle their in-cuts but make their deep cuts close to vertical. [And note that the balance will change depending on circumstances – I’m not advocating that every in-cut should be at 45°, I’m just using that angle to give numerical examples of the kind of advantage you can gain.]
There are other problems too. Cutting straight to a sideline is a bad idea because it has a very definite and predictable finish – you have to stop when you get to the line – so the defender can slack off and get their balance for the next cut once it’s too late for a viable throw. Conversely, although an angled in-cut does get less and less threatening as you keep going, there’s not such an obvious point at which you will definitely turn around.
Additionally, in most offences starting your next cut from right on the sideline is likely to be a sub-optimal situation.
Basically, sideways cutting is rarely a good idea. It can make sense if the disc is tight to the line and you’re cutting away from the line for a swing pass (so that your whole intent is to move the disc as far sideways as possible); it can make sense if you’ve cut to the front cone of the endzone and want to cut back across for an I/O pass while staying in the scoring area. Perhaps it makes more sense in MLU on the big wide pitches (anyone want to comment on whether that has been the case this year?). But I can’t think of many others**.
A ten-year-old could do the relevant maths. Don’t cut sideways.