"Getting the ball lower was pretty much what I wanted," Oh said through an interpreter. "That's what I had to do and I delivered, so I'm happy about it. Our team wasn't in a winning situation when I went up to the mound, so my job was just going up there and making the inning as short as possible."
He has succeeded in making his appearances brief. Tuesday was the third time this season Oh struck out the side. Of his 12 one-inning appearances, he has finished nine in 15 or fewer pitches.
It marked the 12th time he hasn't allowed a run or hit during an outing and brought his ERA down to 1.31 in 20 2/3 innings pitched, with 27 strikeouts.
The question now: Is it too good to be true?
Soon he'll start facing teams who have already seen him pitch. Those teams will have video and a better idea of how to attack the Korean reliever.
"Once guys get a couple looks, it can be different," Cardinals manager Mike Matheny said. "But there are also guys you don't figure out. I think his stuff is good enough. You're seeing deception. He's getting awkward swings. They're just not picking it up. I hope that continues."
Even Oh himself isn't sure how it will play out.
"It's too early," he said. "It's still early in the season, so right now, I'm just focused on step by step, game by game."
Nick Krueger is a reporter for MLB.com based in St. Louis. This story was not subject to the approval of Major League Baseball or its clubs.