I've seen it many times over the years of playing, officiating, and spectating that officials will bring in subs (during a blowout game) by simply blowing the play dead and bringing them in (usually after a made basket). I would have no problem with this and haven't encountered a coach that would. I usually do ask the coach when I pass by if they want the subs in. I try to catch both but I don't always get a chance. If I'm not bench-side, I use my best judgment (which some coaches think is lacking anyways
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-Josh