A year ago, the 49ers were getting very little benefit from the 2012 draft.No. 1 pick A.J. Jenkins, a speedy wide receiver, was supposed to help open up San Francisco's deep passing game, but he couldn't even get on the field. Running back LaMichael James was lost on the depth chart. Offensive lineman Joe Looney was hurt, as were several others.As the 49ers made their way to the Super Bowl, they did it largely without contributions from their rookie class (although James, when he finally got a chance to play, performed well).This season, it's a much different story.With the 49ers halfway through their schedule with a 6-2 record, San Francisco has gotten huge contributions from a flock of rookies. Much like general manager Trent Baalke's draft class of 2011 – that included Aldon Smith, Colin Kaepernick, Kendall Hunter and Chris Culliver – this class of 2013 is getting an A grade."They drafted a great group of guys," said first-year linebacker Corey Lemonier, a third-round pick from Auburn. "We're coming in and showing the older guys we're ready to play week in and week out. We're doing a great job."Lemonier, drafted for his potential as a pass rusher, has played very...