"I thought we got a good look in the spring to kind of have an idea of what he would be able to do and just kind of watching how he would think about facing a hitter," Cardinals manager Mike Matheny said. "You could see that his kind of stuff should play, the way that he locates."
Oh entered this season with 357 saves between the Japanese and Korean pro leagues. He had 41 saves last season with Hanshin of the Japanese Central League of Nippon Professional Baseball.
Batters have had a hard time adjusting to the movement on Oh's pitches.
"Those are sort of things that are pretty unique where a guy can adjust to every pitch and throw it a little bit differently," Matheny said. "That's hard for a hitter to make an adjustment to. It takes years of developing your craft to be able to do that and Seung Hwan has been able to do that."
There has been an adjustment period, such as learning after Oh's first appearance in Pittsburgh that it counts as an official mound visit if his interpreter comes out when just the catcher wants to talk to him.
Yadier Molina and Oh have been working on communicating basic strategy without the need for an interpreter. Matheny said there are ways around the communication barrier.
"We have so few Korean-speaking people in this game we could probably have [the interpreter] stand up [in the dugout] and scream at the top of his lungs, so that's always an option for us," Matheny said. "We'll figure this stuff out as we go, but the communication will get clearer as we continue to get more opportunities."
Oh was signed to ease the burden on Rosenthal and Kevin Siegrist, who combined for 149 appearances in late-inning, high-leverage situations last season. Rosenthal has had 214 appearances the past three seasons and made 48 saves last season, while Siegrist's 81 appearances in 2015 led the Majors.
Oh hasn't disappointed.
"We'll continue to keep giving him those big situations, because he's a guy no matter what the situation is, it looks like he has a plan of what pitch that he wants to make, and he does a great job of executing," Matheny said.
Joe Harris is a contributor to MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.