Keenan McCardell, a two-time Pro Bowler, would certainly seem to fit the bill. And the veteran the Chargers acquired just prior to last October's trading deadline is the favorite to seize the role.But McCardell can't outrun Father Time, and some wonder if the 14-year pro has the stamina to be a factor in all 16 games. He was slowed by a bum hamstring late last year, and did very little in the offseason minicamps because of it.The Chargers, though, were likely just being cautious. But his health, at his age, is worth watching.Eric Parker had a breakthrough year last season, setting career-highs in receptions (47), yards (690) and touchdowns (four). Parker is fearless, which is good and bad for the Chargers.They love his tenacity in going up for passes in traffic, but there's concerns his 6-foot, 180-pound frame can take the punishment.Reche Caldwell is another candidate. After a solid start last season, a serious knee injury derailed his year. How fast he rebounds - so far, so good - is a key.And what about newcomer Vincent Jackson? Although the second-round pick won't be in the running to be the top receiver, his sturdy body and athleticism can't be overlooked. Same goes, though, for him trying to make the jump from Division I-AA Northern Colorado to the NFL.