Despite Brock Purdy and George Kittle missing significant time with injuries last year, the 49ers still managed to field a top-10 scoring offense in the NFL. Purdy is on track for the season opener, and the club is optimistic that Kittle, recovering from an Achilles injury, will either be ready for Week 1 or soon after. 49ers quarterback Brock Purdy is on track for the season opener after missing eight starts last year due to injury. Getty Images Getting both players back for the bulk of the season will provide a huge lift for a team with Super Bowl aspirations. Especially after Kyle Shanahan and John Lynch used free agency to add veteran wide receivers Mike Evans and Christian Kirk. Here is a look at where things stand with the 49ers’ offensive depth chart after free agency and the draft : Quarterback Starter: Brock Purdy Reserves: Mac Jones, Kurtis Rourke, Adrian Martinez The skinny: When healthy, Purdy has shown he can be a top-10-caliber quarterback. The key is to keep him healthy.…