Lynn finished his first half with a 3.41 ERA and 11–4 record in 17 starts. Subsequently, he was named to his first All-Star Game. However, he scuffled with a 5.23 ERA in his next eight starts, and was removed from the rotation. Joe Kelly replaced him in the rotation. Through his first 25 starts, he was 13–5 with a 3.93 ERA. His August ERA ballooned to 6.66 and his second-half ERA overall was 4.32. Lynn attributed his inconsistency to weight gain and poor conditioning. He finished the regular season with an 18–7 record and 180 strikeouts, 3.78 ERA in 35 games, 29 starts and 176 innings. His 9.2 K/9 rate placed fourth in franchise history. He placed second in the NL in wins, seventh in winning percentage, and fourth in K/9. Lynn was added back to the rotation in the NLDS against the Washington Nationals after the team shifted Jaime García to the DL due to a rotator cuff injury. He was the Game 5 starter in the NLCS against the San Francisco Giants, in which the Cardinals held a 3–1 series lead. However, he gave up four runs in innings as the Cardinals eventually lost the series.