article_snippet: ESPN reported The linebacker was retiring over health concerns related to head trauma, an issue that has rattled the league and prompted a massive lawsuit against NFL. '
article_snippet: The linebacker was a consummate professional from day one,' 49ers general manager Trent Baalke said in a statement. '
article_snippet: An ankle injury in December ended his season.
article_snippet: The third-round NFL Draft choice said his was being 'proactive' despite feeling 'as sharp as I've ever been.'
article_snippet: his announcement comes as an unexpected blow to the 49ers, who have already had a difficult off-season and also saw standout linebacker Patrick Willis retire last week.
article_snippet: Monday Morning Quarterback's Andrew Brandt mentioned that this announcement might allow other players to be more open about concussions.
highlights_snippet: The linebacker had two concussions prior to making The linebacker announcement .
  