This is just my opinion, feel free to list your own.
Here are some guidelines for how I made this: I considered how much losing a player to injury would hurt his team, or how much pure value he brings through his level of play. I also forced myself to name at least one player from each franchise, kind of like the all-star game in baseball.
#1: Russell Wilson - Easy call. Wilson is a present and future MVP candidate.
#2: Colin Kaepernick - With Alex Smith traded, Kaepernick is now the player SF can least afford to lose.
#3: Justin Smith - SF's defense kind of embarrassed itself after Smith got hurt last year. I knew he was good. I didn't know he was that good.
#4: Chris Clemons - We've known for years that without Clemons, we're screwed. Then the got confirmation during the Atlanta game.
#5: Earl Thomas - Without Thomas we are probably in big trouble, but until he misses a game, we won't know exactly how much.
#6: Richard Sherman - Someone smart figured out that Sherman's 2012 performance was worth $16 million. That much value from a corner is ridiculous.
#7: Chris Long - He's even better than Chris Clemons, but the Rams (tied for league lead in sacks) depend on him less.
#8: Patrick Willis - He's on a HoF trajectory, though the 49ers could probably survive his absence.
#9: Aldon Smith - He probably isn't as bad as he was after Justin Smith went down last year. He's not elite, but he's still a big time asset for SF.
#10: Dave Zastudil - Arizona's present and future team MVP candidate. His name also kind of sounds like "Disasterville", which is pretty cool.