TOKYO -- Roki Sasaki has the type of pure stuff a team can dream on -- and several did this past offseason. But as both he and the Dodgers have made clear, the 23-year-old right-hander remains a work in progress, which was evident in his first big league start.

Sasaki struck out three across three innings of one-run ball, but he struggled with his command against the Cubs in Wednesday's 6-3 win at Tokyo Dome, issuing five walks and landing only 25 of his 56 pitches for strikes.

Ranked MLB Pipeline's No. 1 overall prospect in baseball, Sasaki brought staggering expectations when he was posted for Major League teams this past offseason as an extremely talented -- and controllable -- arm. While the Dodgers are high on his potential, the team is also aware that he's not a finished project and could have some bumps in the road as he transitions to the Major Leagues.

"I think when you get youth and talent, which is Roki, what that introduces is variance," manager Dave Roberts said before the Tokyo Series finale. "There's going to be some really high highs, and then some things that you just don't know that are gonna happen because of his inexperience."

After four years with the Chiba Lotte Marines -- in which he went 29-15 with a 2.10 ERA and 505 strikeouts in 394 2/3 innings -- Sasaki (23 years, 136 days) became the third-youngest Japanese player to make his MLB debut after playing in NPB. Only Masanori Murakami (20 years, 118 days in 1964) and Tomo Ohka (23 years, 123 days in 1999) were younger.

"I think it was a really good thing that I was able to pitch with a good nervousness," Sasaki said, with director of baseball product development Yuji Akimoto interpreting. "I think it was a really excellent environment created by the Japanese fans, an environment that's unique to Japan. … It was a really good thing to be able to pitch in front of the fans here in Japan."

Sasaki came out firing on Wednesday night, hitting 99.5 mph on his first pitch. Eight of his 11 pitches in the first inning registered at 99 mph or higher -- but he didn't reach that same velocity again in the remainder of his outing.

He retired the first three Cubs batters in order, getting two flyouts to bookend his first Major League strikeout. Sasaki's countryman, Seiya Suzuki, was the first of many to come.

Sasaki's struggles with command began in the second inning, when he issued his first two walks of the night. He escaped that jam without permitting a run, but the Cubs mounted a one-out rally against him in the third. Sasaki allowed an infield single, then walked three consecutive batters to force in a run.

"We made him throw strikes, and he struggled a little bit with that," Cubs manager Craig Counsell said. "The stuff is really good. But I thought we did a good job of executing our game plan."

With the bases still loaded, Sasaki froze Michael Busch with a four-seamer and got Matt Shaw to swing through a slider to get out of his final inning. Sasaki only threw four sliders -- a pitch that is considered more of a work in progress for him -- but the two that drew swings were whiffed on.

"I think there was some nerves, understandably so," Roberts said. "The velocity was good. But I thought the command -- I think the emotions, the adrenaline, was hard to reign it in. But in that third inning, he made some big pitches for us."

Sasaki got just two swings against the 15 total splitters he threw, which came as somewhat of a surprise because he had generated a lot of swing-and-miss against big league hitters with his signature offering during spring. He struggled to establish it in the strike zone early on, and the Cubs batters weren't biting.

"That wasn't something that I had an issue with in my previous Spring Training outings," Sasaki said. "So in some ways, it was a good thing to have that issue come up today. … I want to make sure that I have solutions based on the environment that I'm in and self-correct."