If you have players with stamina below 5, it's very worthwhile to train stamina. It will keep dropping so it's necessary to train it at some point, and Allstar/offseason is the best time to do it. Free throws are important too; there's many a game in which a team with bad FT% will miss 10+ FT's. A couple of training will net you a couple of points per game, so that's an easy improvement too. With both, the effect is bigger if the skills on your players are low, I usually take 5 as minimum target.