here are the monthly splits of starters' ERA, relievers' ERA, OPS and the record for each month:
month record starters ERA relievers ERA OPS
april 14-14 4.74 3.54 .666
may 15-13 4.43 3.94 .740
june 17-11 4.70 3.24 .770
july 15-10 4.28 5.21 .802
august 17-12 3.09 4.13 .771
sept 11-15 4.92 3.68 .739
To quote Meatloaf, a brief descriptive one liner for the Twins' season would be "two out of three ain't bad". When two of these indicators were at or above the league average (.749 OPS, 4.44 Starter ERA and 4.10 reliever ERA) the Twins were winning... When 2 of these indicators were below those averages the Twins were losing.
What caused the September collapse? Sub-par hitting, but mostly sub-par starting pitching.
In the monthly break downs the bullpen had only one month (July) below league average, the starters had 3 (April, June, September) and the batters three (April, May, September). So while the ousting of Livan Hernandez (and his replacement with Liriano) and Bass and the call up of Mijares, gave a big breath for the bullpen in August and especially September and in August for the rotation, the inability to replace Mike Lamb with a productive bat (Brian Buscher's OPS in September was .578) and the inability of Gardenhire to go with the hot bats, cost this team.
To expand on the last point: If one of the two lagging factors (starter ERA or team OPS) ware close to league average in September, the team would have had a better chance to win that month. Given that the starters ran out of gas and there were not many replacement options, better attention should have been paid to keep the hot bats in the lineup.
- As said, Buscher had an .578 OPS in September, but had 55 plate appearances, while Brandon Harris who had .878 OPS for the month, had 44 plate appearances.
- Nick Punto had a .653 OPS in September but was preferred (93 PA) over Adam Everett (.764 OPS, 11PA) and Matt Tolbert (.897 OPS, 33 PA).
- Similarly, Alexi Casilla finished September with .574 OPS and 113 PA; some of those should have been taken by Tolbert
- At DH, Michael Cuddyer with an injured foot and a .667 OPS in September (20 PA) and Kubel (.777 OPS) in September (77 PA) took ABs against LHP from Randy Ruiz who had only 14 PA in the month, even though he posted a .790 OPS the previous month