The Oakland As, which earlier this month acquired Jason Hammel and Jeff Samardzija, are clearly all-in for this season after trading for Boston Red Sox starter Jon Lester. They now have a bona-fide playoff ace.

Lester heads to Oakland with a 2.83 ERA, a 2.62 fielding-independent pitching (FIP) and 9.38 strikeouts per nine innings, helping him accumulate the third highest wins above replacement among starters qualifying for the ERA title.

We can trace some of the improvement to a heavier reliance on the cutter and four-seam fastball at the expense of his sinker.


This has helped Lester gain a greater command of the strikeout zone while keeping runs from crossing the plate.

Jon Lester (Source: Fangraphs)

Even before the trade, the A’s had the lowest starter’s ERA in the American League at 3.32, with the only other AL team below 3.60 their division rival Seattle Mariners. Here is how the rotation looks now, with ERA+ telling us how much better (or worse) the league was than the pitcher. Higher number indicates a better pitching performance.

Lester also finds another gear in the playoffs. He is 6-4 overall with 8.8 strikeouts per nine innings and a 15.00 (!) strikeout -to-walk ratio. In the World Series he is 3-0 with just one earned run in 21 innings pitched.

The latest ZiPs projections have Lester going 5-3 with a 3.36 FIP and 1.5 WAR (tied for sixth best) the rest of the season. That should be enough to make the As, who were the second favorite to win the World Series (15.0 percent) behind Detroit (16.2 percent) before the trade, the undeniable favorite to win it all.