Back in early November, 49ers running back Anthony Dixon was frustrated about his lack of playing time, and unleashed his feelings on Twitter.After not playing on offense in the 49ers' loss to the Saints and losing his spot on the kickoff-return team to LaMichael James, Dixon posted several angry (and punctuation-challenged) tweets, including:"Jus flat outright salty right now WTF praying for more opportunities"; "It jus sucks to have major skill and not allowed to show it wishing the hating would stop smh"; and, "I know I'm a threat I know my game is ready to dominate at the highest level. …"Well, now Dixon might get his chance.Dixon, a special-teams ace and short-yardage power back, is first in line to replace starting fullback Bruce Miller, who's likely gone for the rest of the season after suffering an injury to his scapula (shoulder blade) in Sunday's victory over Tampa Bay.After Miller was injured, Dixon filled in for him the remainder of the game, and would be the most logical long-term solution for the 49ers to fill Miller's spot for the remaining two games of the regular season and into the playoffs.Miller, a converted defensive end from Central Florida, has been a...