49ers' roster takes shape with trade, release

The San Francisco 49ers' initial 53-man roster began taking shape around the edges Friday with a moves related to special teams.

The team traded backup safety Colin Jones to Carolina. San Francisco will reportedly receive a seventh-round choice in return, presumably from 2014 or later given that the Panthers traded a 2013 seventh-rounder to Oakland for Louis Murphy.

2011 Special-teams Snaps: 49ers

The 49ers also released veteran fullback Rock Cartwright, a player the team signed after losing 2011 special-teamer Blake Costanzo to Minnesota in free agency. Cartwright, 32, played more than 60 percent of the special-teams snaps for Oakland last season. He spent much of his career with the Washington Redskins, including when 49ers general manager Trent Baalke worked for the team.

These moves suggest running back Anthony Dixon showed enough to stick as a backup running back and core special-teams player. Dixon's status appeared tenuous when the 49ers signed Brandon Jacobs in free agency. Jacobs appears likely to supplant Dixon in short-yardage situations. Dixon volunteered to play fullback during training camp. He ran effectively during preseason, making a strong case to stick with the team.

As the chart shows, six of the top eight contributors for special-teams snaps from 2011 remain with the team following the departures of Costanzo and Jones. That could change before and during the regular season, of course. NFL teams must reduce their rosters from 75 to 53 players by 9 p.m. ET Friday.