If the Blue Jays are going to make a real run with a patchwork rotation weathering several injuries, they’ll need the supporting cast to steal the show. In Wednesday’s 9-1 win over the Red Sox at Sahlen Field in Buffalo, N.Y., Shun Yamaguchi was that unlikely star.

Toronto’s lineup just keeps rolling at its 2020 home, too, where the heavy rains through the game couldn’t cool off Rowdy Tellez. The slugging first baseman launched two more home runs -- neither in doubt -- and went 3-for-4 with four RBIs.

• Box score

Specifically, how the Blue Jays won on Wednesday mattered, though. In a bullpen game, with another planned for Friday, they needed someone to step up and chew through innings. Julian Merryweather was excellent in the “opener” role with two scoreless innings, as he continues to emerge as another legitimate arm in this deep Toronto bullpen, but the four innings Yamaguchi gave the team behind Merryweather should change the narrative on his season altogether.

After a rocky Spring Training and Summer Camp, Yamaguchi’s introduction to MLB wasn’t exactly a soft landing. His first two appearances came in extra innings, with a man already standing behind him on second, and he racked up two losses with just one inning. Yamaguchi deserves far more credit than he’s gotten, though, as he’s been a completely different pitcher in August.

“I think he’s getting used to the baseball here in the States, because his splitter is just nasty now,” said manager Charlie Montoyo after the win. “Of course, he’s locating his fastball now, too, but before, in his first couple of outings, his splitter wasn’t doing much. Now, it’s nasty. That’s made a big difference.”

When Yamaguchi signed a two-year deal in the offseason to join the Blue Jays out of Japan, that splitter was billed as his headlining pitch. It was moving too much on him at times in Spring Training, as he adjusted to a slightly different ball in MLB, but he’s found it now.

Yamaguchi needed 59 pitches to cover his four innings of one-run ball, with two strikeouts and two walks. The Blue Jays are trying to get one of their long relievers stretched out to a starter’s length while still competing day to day, which is a fine balance they’re not entirely in control of, but Yamaguchi is making a strong case to be considered given the injuries to Nate Pearson, Matt Shoemaker and Trent Thornton. Once a closer in Japan, Yamaguchi later stretched out as a successful starter, so there aren’t many roles he hasn’t succeeded in professionally.

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Pitchers thrive on routine, though. Yamaguchi entered camp competing for the No. 5 rotation job, which has changed along the way. He’s adapted to a new league, team and country under extremely unique circumstances, and it’s now easier to see how a defined role has helped Yamaguchi.

“It’s a little different from being a starter and starting the game, so there are small adjustments I have to make,” Yamaguchi said through an interpreter. “Going back to today’s outing, every time I went back to the dugout, I spoke with Reese [McGuire]. We had pretty good communication. The stuff I used to do in Japan was pitch down. Those are the things I have discussed with Reese, and things went well from there.”

The Blue Jays will send ace Hyun Jin Ryu to the mound for Thursday’s finale against the Red Sox, a game in which they’ll be looking to get seven innings or 100 pitches from a starter for the first time this season. Yamaguchi’s innings Wednesday are part of the solution, but Toronto needs innings -- and quality ones -- anywhere it can get them with Monday’s Trade Deadline fast approaching.