Things are looking up for both Greg Jennings and Dimitri Nance.  After not participating in practice Wednesday, Jennings was limited Thursday but took part in several team drills, working through a foot sprain suffered on his first catch last Sunday in Atlanta.  Jennings said he still experiences some discomfort but he has no doubt he'll be available against the 49ers.  Greg was walking on air anyway, his wife Nicole delivered their third child and third daughter Wednesday night.  As for Nance, he's been cleared to practice after suffering a concussion against the Falcons.  Passing a series of medical tests for practice should pave the way for him to be on the field against San Francisco.  Two players were downgraded Thursday, Ryan Pickett (ankle) and Charles Woodson (toe) went from full participation to limited but both are expected on Sunday.  Chad Clifton (knee) and Cullen Jenkins (calf) went from limited to full participation.