The best-case scenario for the San Francisco 49ers in the draft does not involve trading into the top five picks of Round 1.
In a recent mock draft, Don Banks of Sports Illustrated had the Niners trading up to the fourth pick for former USC defensive tackle Leonard Williams, a good player. He would make a fine replacement for Justin Smith if he retires.
The Niners should not trade into the top five for Williams or anyone.
Trading into the top five would cost them their first-round pick, their second-round pick and maybe more.