San Francisco 49ers running back Marcus Lattimore chatted with ESPN readers Friday morning. Here are some highlights:Scott from SD: Die-hard fan here in South Dakota, Marcus. It's cold here. COLD. How is the knee holding up? Toughest part -- physical rehab or mental rehab?Lattimore: The knee is holding up great. It feels good. It's felt better than I have before. The past few months, I haven't had any swelling or anything. The mental part is the hardest.