Ambry Thomas is the one defensive back the 49ers drafted this year who deserves lofty expectations.
The 49ers drafted him in Round 3, he's 6'0", he runs a 4.3 and he returns kickoffs as well. He's an extremely dynamic athlete -- exactly what you're looking for a cornerback.
Initially, he'll be the 49ers top backup cornerback. If Jason Verrett gets injured, Thomas would replace him on the outside. And if K'Waun Williams gets injured, Thomas would replace him at nickel.
And Thomas has so much ability, once he fills in for an injured defensive back, he might never give up the job.
It seems the 49ers drafted Thomas to replace Verrett next year when Verrett is a free agent. In the meantime, the 49ers don't need Thomas to start, because they have Verrett and Emmanuel Moseley.
It's possible Thomas will outplay Moseley in training camp and take the veteran's job before the season starts. But the 49ers just gave Moseley a two-year extension, and he's a solid player. The 49ers know what he can do. And they know they can go to a Super Bowl with him -- he was a starter when they faced the Chiefs.
Unfortunately for Moseley, he also gave up that long catch to Tyreek Hill on third and 15, and was a primary reason the 49ers lost.
So if Thomas takes Moseley's job, good. That would mean the 49ers upgraded from serviceable to better.
But I haven't seen enough from Thomas to say with certainty he'll beat out Moseley any time soon. For now, expect Thomas to be a super backup.