PITTSBURGH -- The Mariners’ callup of Justin Dunn isn’t as tied to his performance as it is to him getting his feet wet as a prelude to 2020.

But after a rough MLB debut last Thursday against the Reds, in which he recorded just two outs (both sac flies) and walked five, Dunn accomplished the task he was given on Wednesday against the Pirates -- get through the lineup once -- while putting up two scoreless innings. Then, the Mariners’ bullpen backed him to beat the Pirates for a second straight night in a 4-1 win at PNC Park. It was the club's fourth straight victory and it marked its third straight series win.

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Dunn’s outing wasn’t without blemishes. He walked three of the nine batters he faced, but those plate appearances were more competitive. He reached a 3-0 count only once and battled Adam Frazier in a seven-pitch plate appearance in the second before the Pirates second baseman drew a walk.

But Dunn crowded the zone a bit more this time, not missing arm-side high as often as he did his first time facing Major League batters. Though pitchers aim to stay away from throwing center-cut pitches that could be stroked, aiming there was Dunn's plan.

“Basically, throw it down the middle and go from there,” said Dunn, ranked by MLB Pipeline as the Mariners' No. 5 prospect. “Last time out, I wasn’t really around the zone, so we couldn’t really see how my stuff played. Attack the zone, fill it up and see if we can get some outs.”

The night ended with a career mark for the 23-year-old, when he notched his first Major League strikeout against Pirates pitcher Dario Agrazal. Dunn threw 36 pitches (19 strikes) before being replaced by Tommy Milone, who tossed five scoreless innings and gave up just two hits on just 51 pitches.

What were the keys to Dunn settling in a bit more?

The first: breathing. The second was a bit more odd. Dunn was pleased to see Bryan Reynolds, who owns the highest batting average among National League rookies this season, in the Pirates’ lineup. Reynolds drew the first walk off Dunn, but just seeing a familiar name on the opposing squad -- Dunn faced Reynolds, a Vanderbilt product, while at Boston College -- calmed him down.

“It kind of put things into perspective and I realized we were just playing the same game, just on a bigger stage," Dunn said.

Simply being able to return to his usual process of preparation was a help for Dunn, too. The Mariners' coaching staff coached him and fellow rookie Justus Sheffield about getting back into routines, Dunn said, a breakdown that featured insight about 2018 NL Cy Young Award winner Jacob deGrom.

“That’s how I am. I’m a very routine-based person to the T of what I do each day,” Dunn said. “And this week, I was able to kind of fall back on my routine and kind of have the confidence knowing that, ‘OK, I’ve done my work. That’s done me well all year, so all I have to do is go out there and pitch.’ That worked out today, but still some room for improvement.”

Mariners manager Scott Servais and his staff were aware that Dunn had a Minor League season under his belt, but that Dunn hadn’t pitched deep into September before. They’ll continue to give him the ball every fifth or sixth day until the regular season concludes next Sunday -- meaning Dunn will make one or two more starts -- but the club won't necessarily increase his output.

“It was not to see how deep he could go, what kind of endurance he’s got, anything like that. Can he get through a lineup two or three times? That’s not what it’s about,” Servais said. “It’s about just getting him indoctrinated at the big league routine of going through and preparing for a start, so that’s the goal here and we’ll stick with it.”

More Mariners history

Another Mariners prospect continued his streak at the plate behind Dunn. Kyle Lewis swatted his fifth homer in just his eighth big league game, setting a franchise record for the most homers in a player’s first eight games. Lewis also tied for the second most in MLB history through eight games, trailing only Trevor Story’s seven set for the Rockies in 2016.

“Always an honor being able to do things that are kind of groundbreaking. That’s always cool. I’m sure looking back on it, I’ll be able to reflect on those kind of things down the road. But right now, I’m just in the moment.”

Lewis, the club's No. 10 prospect, has 10 hits in the Major Leagues so far, and each has been crushed with an exit velocity of 100 mph or higher, per Statcast, which classifies anything 95 mph or higher as hard-hit. Lewis' homer on Wednesday rocketed 102.1 mph off the bat.

“I’ve got good size, so it’s going to come off hard naturally,” Lewis said. “Just trying not to manufacture that and let it happen.”