SEATTLE -- So much for the arm soreness that cut George Kirby’s most recent outing short.

Kirby carved his way through the D-backs for a career-high 12 strikeouts over seven scoreless innings on Saturday night at T-Mobile Park, lifting the Mariners to a 3-1 victory to clinch their fourth straight winning series.

Six days after Kirby felt minor arm soreness and departed after five scoreless innings and 88 pitches at Coors Field, he was in peak form -- and not just in the box score. Kirby came out firing his four-seam fastball harder than he has all season, generating seven whiffs among the eight total swings in the first inning, when he struck out the side exclusively on heaters.

From there, he was off and running. Kirby topped out at 99.3 mph, his fastest pitch of the year and strike three to Lourdes Gurriel Jr., and sat at 96.4 mph on the four-seamer, a healthy 1.2 mph uptick from his season average.

Velocity and whiffs have always been part of Kirby’s game, but never like this. And though the game plan with catcher Cal Raleigh called for a heavy dose of heaters, they doubled down once they realized what they were working with.

“It was spinning pretty good,” D-backs manager Torey Lovullo said. “Early on, it was 2,500 [rpm] and throughout the course of the game, it was pretty close to that. And it came out hot, came out aggressive. Like I said, some guys made some adjustments, others didn't.”

Kirby generated a career-high 23 swings and misses, including 18 on the four-seamer. But his best pitches of the night were arguably those that didn’t generate swings at all -- a pair of front-door two-seamers to lefty-hitting Corbin Carroll and Ketel Marte for backward K’s that were painted perfectly on the inner black. He also used the slider and splitter for a strikeout apiece, both to lefty Joc Pederson.

“I was glad Cal called those,” Kirby said of the two-seamers. “We haven't really seen much of those the last four or five games. I was glad that we had some front-hip candidates tonight.”

Kirby is the fifth pitcher in the Majors this season with at least 12 strikeouts, but the first with two or fewer hits in that start. His only damage was via a 113.9 mph single to Christian Walker that ended a 12-pitch at-bat in the second, and a double off the yellow padding on the right-field wall from Blaze Alexander in the third. That was followed by a four-pitch walk to Jake McCarthy to create the night’s only real threat, and he followed both sequences with consecutive strikeouts to end each inning.

Kirby finished his night by retiring each of his final 14 batters and extended his scoreless streak to 14 innings.

“When you've got guys like Walker and Marte just swinging through fastballs, those are really good hitters,” said Ty France, who crushed a two-run homer in the seventh. “So to see them swinging and missing like that and looking up at the board seeing 99 [mph], that was pretty special.”

Moreover, Kirby has allowed two runs with 25 strikeouts over 18 innings (1.00 ERA) across his past three starts. That followed 13 runs and 18 hits with just five strikeouts in 7 2/3 innings (15.26 ERA) over his previous two outings. His turnaround has tied into that of Seattle’s overall rotation, which extended its franchise record to 15 straight games with two earned runs or fewer.

In this run, Mariners starters lead the Majors in ERA (1.46) and WHIP (0.81), rank second in opposing OPS (.525) and hits-per-nine-innings (5.17), third in strikeout-to-walk ratio (4.41) and fourth in total strikeouts (97). Kirby’s outing was Seattle’s American League-leading 16th quality start of the season, over which the club is 14-2.

Thanks to run support via consecutive hard-hit balls from Mitch Garver and Luke Raley in the fifth and France’s decisive insurance homer, the Mariners have won nine of their past 11 and an AL-best 11 of their past 15, climbing to a season-high three games above .500 (15-12) and into first place in the AL West for the third straight day.

“I don't think we're at our best yet,” France said. “Once we get our one-through-nine clicking in the lineup, it's going to be dangerous. So I'm excited for that.”