SANTA CLARA -- Cornerback Perrish Cox will help the 49ers compensate for season-ending injuries to Kyle Williams and Kendall Hunter.Ted Ginn will continue to handle the main duties on kickoffs and punts. Cox has been tabbed as the team's new backup return man, he told CSNBayArea.com on Friday, just prior to the 49ers' departure to play the St. Louis Rams.Williams and Hunter are the only other players on the roster who have returned kicks this season. Williams led the 49ers with averages of 13.0 yards on four punt returns and 27.2 yards on 13 kickoff returns.Hunter averaged 23.6 yards on seven kickoff returns. Ginn has averaged 10.6 yards on 25 punt returns and 23.0 yards on 11 kickoff returns.Williams (left knee) and Hunter (left Achilles) were placed on injured reserve this week and are officially out for the season."I really feel bad for both of those guys," Cox said. "Now, I have to step up whenever I'm called on."Cox, who did not have any kick returns in the exhibition season, has been practicing punt and kickoff returns all season, he said. He returned kicks with the Denver Broncos in the 2010 regular season and in training camp the following year. In 2010, he averaged 2.3 yards on three punt returns, with a 19.1 average on nine kickoffs.Rookie running back LaMichael James has been listed on the 49ers' depth chart as the No. 2 man behind Ginn on both kickoffs and punts. James has not been active for a game this season.Coach Jim Harbaugh on Friday declined to comment on the team's backups on punt and kickoff returns. Harbaugh did reveal, however, that Ginn takes over for Williams as the team's emergency quarterback. Ginn played quarterback in high school.With David Akers limited this week in practices due to a pelvis injury, Harbaugh said the emergency kicker is Andy Lee or Isaac Sopoaga. Akers has been cleared to play Sunday.