When the 49ers used their No. 1 pick to take wide receiver A.J. Jenkins in the 2012 draft, it was hoped Jenkins would become the team's deep threat.Instead, he couldn't get off the bench and was traded away.Over the past two years, the Niners also have had similar hopes for Ricardo Lockette, Mario Manningham and Jonathan Baldwin, among others. But each hasn't been able to fill the role of a speedy, deep-threat wideout who can stretch defenses.Now, with the emergence of the Seattle Seahawks, the 49ers need such a receiver more than ever.Going into 2014 the 49ers have two excellent, proven pass catchers in Michael Crabtree and Anquan Boldin, and a young receiver they like in Quinton Patton. But none of those three has the blazing speed that would force the Seahawks secondary to respect the deep ball. Seahawks 12th Man Flag to Torment 49ers Fans As Matt Barrows of the Sacramento Bee wrote this week, one of the keys for 49ers GM Trent Baalke is to find a downfield wide receiver who can "force Seattle's talented safeties off the line of scrimmage." As Barrows noted, Seahawks safety Kam Chancellor had a monster game in the Super Bowl against Denver because he could play up close against...