Backgrounds can be more distracting during the day as the light falloff at night renders most of the background too dark to be distracting. Accordingly, a wide aperture is needed to blur the background. I find that anything slower than f/2.8 results in too great a depth of field and the shots look like they were taken with a point and shoot camera.
So, you need f/2.8 under the lights to get a fast enough shutter speed to stop the action at an acceptable ISO setting and you need f/2.8 during the day to isolate backgrounds. I used various ISO settings so as to keep the shutter speeds generally between 1/1000 and 1/3000 a second. Slower than 1/1000 and a higher ISO was needed and faster than 1/3000 and I could use a lower ISO for better image quality. There are ways to set aperture and shutter speed manually and have an auto ISO setting to adjust the exposure but I haven't played around with that as yet.
|200mm, f/2.8, 1/2000 sec., ISO 800|
|70mm, f/2.8, 1/3000 sec., ISO 800|
|200mm, f/2.8, 1/2000 sec., ISO 1600|
|125mm, f/2.8, 1/1500 sec., ISO 1600|
|120mm, f/2.8, 1/4000 sec., ISO 1600|