After a very productive offseason, 49ers general manager Trent Baalke was very excited about his team's prospects in early July.Through free agency, the draft and the fact several young players would be able to challenge for playing time after sitting out their rookie seasons – such as Tank Carradine and Marcus Lattimore – Baalke told reporters he liked the talent and depth of his group."We feel good, obviously, about the roster as it stands," he said.Less than a month later, however, the 49ers aren't as deep as they once were.They entered training camp already knowing that star linebacker NaVorro Bowman won't be available unitl midseason at the earliest. But since then, running backs LaMichael James and Kendall Hunter have gone down with serious injuries, as has starting nose tackle Glenn Dorsey. Hunter and Dorsey are lost for the season. Now receivers Michael Crabtree and Brandon Lloyd will likely miss a week or two of practice to allow some leg ailments to get right. Plus, right guard Alex Boone is still holding out, which impacts depth on the offensive line.Fortunately, all of Baalke's work has given head coach Jim Harbaugh plenty of options. Rookie Carlos Hyde,...