In larger maps, they just spread out and get picked off one by one. But in Nuketown, there's only three direct paths. If they go one way, you can go the other. Or treat them as bait to flush out the enemy.
Even a noob can protect your flank just by simply acting like a Living Portable Radar that screams when they get shot, alerting you to the enemy's presence. --- The greatest victory isn't by points or kill/death ratios. It's causing your opponent to rage-quit.