"Amid much speculation about the timing of an injury in his first game back, Chargers wide receiver Vincent Jackson's calf strain on Sunday may actually have been precipitated by him trying to be a team player.

According to a source, Jackson tweaked his left calf in practice Friday and then injured the other calf Sunday, likely by overcompensating for the original injury wile trying to play.

Another source said he didn't know of any "tweak" on Friday but that Jackson was sore and "he did more than he should have" in the lead-up to his first game."