Sure it does. If you have a lead, your defense has shut down the other team. Why mess with that chemistry? Unless your defenders have been making major offensive runs, they shouldn't be tired. Besides, I don't know that I'd call Chastain for DiMartino an offensive substitution. If anything, you're putting a bigger, stronger, more experienced player in for an attacking midfielder who was getting pushed around out there (I was at the game). Don't get me wrong, I like DiMartino as a player, but she's a munchkin compared to Averbuch. So when Sawyers put in Averbuch, I think your coach was trying to even up that physical matchup a bit and shut down the middle of the field. Putting Millbrett in late worked for you before, and there's nothing like having a crafty sniper like Millbrett in to pick up a cheap goal against a team that's pressing, trying to score. You can steal a couple of points that way. The thing that surprises me a bit about your team is that you don't START a little more speed in back. Your backs play really smart soccer, but they do have to give fast forwards like O'Reilly and Walsh a bit of a cushion, because they'll never beat them in a foot race. So those two were able to put together a perfect pass and a perfect shot in the seams that their speed created for them. With the attacking players that you have, you should have a lot of fun soccer to watch. When Sinclair gets going, too, look out!
A proper defensive sub while your team has the lead is not replacing a player on the back line - that is rarely done but it is replacing an attacking midfielder with a defensive-minded one or a striker with a midfielder. I don't consider Brandi a defensive sub. She is playing offensively minded. A good sub would have been adding in a player like Abegg in for a midfielder. In the first two games the opposition has scored after he made the exact same subs.