One X-factor for each team in the NFL playoffs:

49ers cornerback Ambry Thomas

San Francisco 49ers – Ambry Thomas

And since we’re talking about rookies, how about another one on the opposite side of the ball from this NFC West team.

I do understand that right guard and tackle are areas of concern as well, but their biggest weakness or at least unproven commodity is their play on the perimeter defensively.

I loved seeing Jason Verrett finally stay healthy for a full season last year.

Since then, the Niners have been vulnerable to teams with legitimate outside receiving threats.

Emmanuel Mosley has been a solid starter for them, but they still need somebody to step up as the left cornerback for them.

The guy who has commanded that role over the past month is Ambry Thomas, playing over 90 percent of snaps in each of their last five games. I was a big fan of his competitive spirit during Senior Bowl practices and liked what I saw on tape.

The lack of height and length made him a projection for the slot – where he rarely lined up in college – but his skill-set matches well with all the two-high safety shells from San Francisco.