Smith did not start, but did make his NFL debut against the Seattle Seahawks. In Week 4, against the Philadelphia Eagles, he recorded his first sack on Michael Vick. In the next two weeks, Smith would win the Pepsi NFL Rookie of the Week in victories against the Tampa Bay Buccaneers and Detroit Lions. After a strong October, Smith became the first 49ers player since linebacker Patrick Willis in 2007 to earn the NFL Rookie of the Month, he recorded 13 tackles, 6. 5 sacks including one that forced a safety as he helped the 49ers to a 6-1 record. In Week 15, Smith recorded 2. 5 sacks against the Pittsburgh Steelers. He also surpassed Charles Haley for the 49ers record for most sacks by a rookie in a single season with 13. 0 sacks. He finished with 37 total tackles, four pass deflections, two forced fumbles, and 14 sacks. Smith was half a sack shy of tying the all-time rookie sack record held by defensive end Jevon Kearse despite not starting a single game in his rookie season. He was named Defensive Rookie of the Year by Pro Football Writers of America, and finished second to Von Miller for the Associated Press NFL Defensive Rookie of the Year Award.