SEATTLE -- When it comes to what matters most in this Mariners’ season, priority No. 1 is the development of the young core of prospects making their MLB marks this season. That made Saturday’s 10-1 victory over the Rangers most satisfying for a Seattle club that started six rookies.

First baseman Evan White returned from a two-game absence due to a bruised left knee and unleashed a 2-for-5 night with a home run, a double and six RBIs. Center fielder Kyle Lewis continued his rookie crusade by reaching base five times while going 3-for-3 with a double, two walks and three runs scored to hike his batting average to .373.

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Left fielder Sam Haggerty checked in with a 2-for-5 night and scored a run, as the recent callup has gone 5-for-17 (.294) in his first four games, and Jake Fraley scorched a double and scored a run in his season debut in right field after being promoted from the alternate training site prior to the game.

The offensive punch was welcomed by fellow rookie Justus Sheffield, who pitched six innings of one-run ball to even his record at 2-2 with a 3.51 ERA in five starts. Rookie relievers Joey Gerber and Aaron Fletcher -- who became the eighth Mariner to make his MLB debut this season -- helped close out the win, as Seattle improved to 10-19 and handed the Rangers (10-16) their seventh straight loss.

“We’re learning and we’re growing,” Mariners manager Scott Servais said. “It’s fun when guys go out and play like this.”

Here’s a closer look at four rookies who stood out the most on Saturday:

White looks all right
The 24-year-old first baseman sat out Thursday and Friday with a bruised left knee, but he returned with a six-RBI breakout that tied Willie Bloomquist’s 2003 franchise record for most runs driven in by a rookie in a single game. After opening eyes early with his dynamic defense, the '17 first-round Draft pick is starting to heat up with the bat and has four homers in his past six games.

White’s two-run double got things started in the first inning, and his three-run homer in the third broke the game open.

“Evan has made a few adjustments,” Servais said. “It really started on the last road trip. The impressive thing on the home run, on a fastball inside, he kept the hands inside it and kept the ball fair and hit it out of the park. That’s not easy to do. That’s the kind of talent he has. It’s nice to start to see him getting results. We’re starting to see all the talent come out at the plate.”

Lewis keeps raking
There aren’t many players in the Majors performing better than Lewis at this point -- and that’s not just among rookies. The 25-year-old is 13-for-23 during a seven-game hitting streak and now is second in MLB behind only Colorado’s Charlie Blackmon with his 38 hits this season, third behind the Yankees’ D.J. LeMahieu and Blackmon with his .373 average and third behind the Cardinals’ Paul Goldchmidt and Phillies’ Bryce Harper in on-base percentage, at .463.

“That guy is about as focused as anybody we have in the clubhouse,” Servais said. “One of the coaches asked me on the bench tonight if I’d ever seen a rookie come in and put something like this together. I said, ‘Yes, I have. I had the chance to play with Jeff Bagwell his rookie year in Houston.’ Same type of stuff. Just locked in, a ton of confidence and staying in the moment. It’s a really good spot he’s in, and we have to keep him in that spot for as long as we can.”

Fraley joins the fight
The Mariners’ No. 10 prospect made his 2020 debut in right field after being called up from the alternate training site and went 1-for-3 with a double and a walk. The double had an exit velocity of 112.2 mph, which made it the hardest-hit ball by a Mariner so far this season, surpassing White’s 111.1 mph max, Lewis at 110.9 and J.P. Crawford at 110.1.

There have only been 38 balls hit harder in MLB this year than Fraley’s third-inning scorcher to right-center, per Statcast.

“Jake had some really good, competitive at-bats,” Servais said. “The double he hit, that’s what Jake Fraley can do. We’ve always liked the bat and the player. Just to get him going and see his confidence growing would be really huge for us. He’s going to get a chance to play. We’ve had a ton of injuries. The opportunities are there for a lot of guys, so he’ll continue to get his chances.”

Sheff keeps cookin’
The progress of Sheffield over his past three starts has been among the most promising developments for a Seattle squad that has a bundle of interesting pitching prospects still waiting in the wings.

Acquired from the Yankees in the James Paxton trade in December of 2018, the 24-year-old has found his stride over his past three starts, going 2-0 with a 1.00 ERA, 16 strikeouts and two walks in 18 innings against the Rockies, Astros and Rangers. He held Texas to one run on six hits over six frames in an 85-pitch effort.

“Get ahead, stay ahead,” Sheffield said. “That’s big. My last couple outings, I’ve been able to do that.”

Sheffield also had the perfect delivery on his teammate Lewis.

“Rookie of the Year,” Sheffield said. “That’s all I’ve got to say.”