Going into each matchup, you want to set the lineup that you think will get you the most possible points. That’s just common sense. However, sometimes you need to make adjustments on Sunday after the early games are underway. If your opponent comes out hot, and all of his guys are putting up big numbers, then you may need to make some changes to the guys in your lineup whose games have not yet started. You have a lot of ground to make up, so you might as well take out the safe RB and put in the one who could go off and get you back in contention. It’s worth putting in your risky guys when you’re far behind.
I’m a big advocate for adding high-risk, high-reward guys and also starting them, BUT if your matchup is underway, and the early games are already over, relook at who is left to play from your team and also your fantasy score. If you’re up 25 points, and you and your opponent both have just one player left, this is when you should take your high-risk guy out of the lineup and put in someone who you know will get you a decent point total. These numbers are arbitrary, of course, so each situation has its own circumstances, but, as a general rule, go for the less risky option if you’re already up big. The last thing you want is your boom-or-bust player getting 1 point and you losing the week.