The San Francisco 49ers opened the week of practice on a rainy Thursday afternoon in Santa Clara missing one of their key offensive playmakers, tight end George Kittle. Kittle, who injured his toe in the 49ers’ NFC championship game against the Detroit Lions, did not participate in Thursday’s practice. Head coach Kyle Shanahan described the injury as “just a toe” and indicated earlier in the week that his veteran tight end is expected to be daily this week.Aside from Kittle, the team only had two other players on the injured list last week. Cornerback Ambry Thomas is dealing with an…