Seattle essentially didn't leave its nickel package and still shut down the 49ers' run game late last season. A big SF problem: They didn't have a healthy plus-WR to threaten any separation that could, in turn, space the run game. A healthy Ricky Pearsall actually tilted the Week 1 game in the 49ers' favor. So both of these guys, whom SF didn't have last season, will be key for very specific reasons: Mike Evans for spacing and perimeter blocking — making running vs nickel more manageable. And Deebo Samuel for his multi-positional versatility: He's strong enough to bruise lighter defensive packages without committing the 49ers to run or pass, regardless of where he lines up. Elite tactical battle coming between Kyle Shanahan and Mike Macdonald. And one has to assume that Brock Purdy's off-schedule ability — which can create opportunities beyond the box that the two schematic masterminds cook up — will be necessary if the 49ers are to pull the upset