One area the 49ers hope to improve on in 2013 is special teams play, particularly on kick and punt coverage.So with that in mind, San Francisco signed some veterans with good NFL track records on special teams, including wide receivers Kassim Osgood and Marlon Moore, safety Raymond "Bubba" Ventrone and linebacker Dan Skuta."We are taking a special teams unit that's been very good, very productive, and seeing if we can't get even better," head coach Jim Harbaugh told the team's website this summer. By adding players with a history of making big special-teams plays, said Harbaugh, "those teams have the chance to be elite."Osgood, in particular, could be a high-impact player.The three-time special teams Pro Bowler, 33, who's played for the Chargers, Jaguars and Lions, made an immediate contribution in his debut for the 49ers against the Denver Broncos in the team's first exhibition game of 2013.On the second-half kickoff, Osgood – who's made a good living making tackles on punts and kickoffs as a gunner – streaked downfield to take down Broncos returner Trindon Holliday at the 6-yard line. For the night, he had two of the 49ers' six special-teams tackles.He also made...