Miller made his MLB debut in 2012 at age 21. He pitched in 6 games, 1 as a starter, went 1-0, 1.32 in 13 2/3 innings, striking out 16 batters in the process. This spring, Miller was locked in a tight battle with Joe Kelly for a spot in the Cardinals rotation. Miller pulled away with a couple good performances late in March to win the job. Miller impressed this season, finishing at 15-9, 3.06 in 31 starts, striking out 169 in 173 1/3 IP. This included a game against the Colorado Rockies where he gave up a leadoff single to Eric Young, Jr and retired the next 27 batters to finish with a 1 hit shutout. Miller contributed heavily to the Cardinals winning the NL Central title, yet he was not counted on during the postseason run, which lasted through the World Series.
Obviously one of the key factors was the Cardinals decision to go with Michael Wacha and Kelly in the postseason rotation. Kelly, who lost the early starting rotation spot to Miller, pitched in 37 regular season games, 15 starts and went 10-5, 2.69 for the Cardinals with 79 K in 124 IP. Wacha, the team's 1st round draft pick in the 2012 draft, got into 15 games, 9 starts and finished with a 4-1, 2.78 with 65 Ks in 64 2/3 IP. Obviously, going to Wacha was an excellent move, as he was the Cardinals best starting pitcher in the postseason. He was 4-1, 3.26 in 5 starts including his rough outing in Game 6 of the World Series. Prior to that, Wacha had given up just 3 runs in 27 innings over the course of his first 4 starts, which included a solid start in Game 2 of the World Series.
With Adam Wainwright (19-9, 2.94, 219 Ks in 241 1/3 IP) and Lance Lynn (15-10, 3.97, 198 Ks in 201 2/3 IP) expected to be part of the Cardinals starting four, the decision was once again between Kelly and Miller. This time the Cardinals went with Kelly, who was not bad, but also not dominant in the 2013 postseason. Kelly made 4 starts, going 0-1, 4.22 which came from the 10 ER he allowed in 21 1/3 innings.
Miller actually got in more postseason games in 2012 (2 in the NLCS vs San Francisco, giving up 2 runs in 3 1/3 IP) than he did this postseason (1 against the Pirates in the NLDS, giving up a solo HR in 1 inning of work.
I thought that maybe Miller did not pitch well in September. I checked his September stats to find out that Miller pitched to a 2.76 ERA (9 ER in 29 1/3 innings) and was 3-0 with 15 Ks. Yes Kelly was better with a 2.10 ERA (8 ER in 34 1/3 IP) in 6 starts, striking out 20 while going 4-2 over that span.
The only conclusion I could come up with was that Miller was on some sort of innings limit. For the season, he threw 173 1/3 innings, while Kelly threw 124 for the season as he pitched in the bullpen for a while. Wacha threw a combined 149 2/3 innings between AAA and the majors this season.
I'd glad to see Miller nominated for NL Rookie of the Year, because he does deserve credit for the season he had. Hopefully next year, the Cardinals will use him as a starter in their postseason.