KANSAS CITY, Mo. — James Paxton didn’t have to wait very long to tell his parents he was headed to the big leagues.

His folks had driven down from Ladner, B.C., to see Paxton pitch for the Tacoma Rainiers on Monday when he was pulled just two innings in. Once in the dugout, he was informed he was joining the Mariners and so, after congratulatory hugs from teammates, he sought out mom and dad.

“I was able to call my dad down and told him in the locker room,’’ Paxton said. “And after the game, we were able to go out and meet. It was very cool being able to have them there and share this experience with them.’’

The left-handed starter — one of the team’s so-called “Big 3’’ prospect arms along with Taijuan Walker and Danny Hultzen — was one of four minor leaguers added Tuesday to the team’s expanded September roster. Seattle also called up pitchers Hector Noesi and Chance Ruffin and infielder Carlos Triunfel, along with coach Howard Johnson.

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Paxton, 24, who went 8-11 with an earned run average of 4.45 in 28 appearances, will start for the Mariners on Saturday at Safeco Field against the Tampa Bay Rays, where his parents will again be able to make the rather-easy three-hour drive south to see him in person. The Mariners will be going with a six-man rotation the rest of the way, with Paxton being a mainstay of that until the season ends.

Taijuan Walker is to pitch here on Wednesday, then next Tuesday in Seattle against Houston. After that, Walker will reach his innings limit for the year and Brandon Maurer will take his rotation spot.

Paxton said it’s been an “up and down” year for him in AAA, but he’s regained some of the command that abandoned him early and has become more efficient with his pitch counts. He said the AAA hitters forced him into it, given their more-disciplined nature.

“Those guys won’t chase quite as much as AA guys will,” he said. “You definitely have to be able to come into the zone and challenge them early in the count. That was the biggest thing I learned this year: trying to get guys out with less pitches.”

Geoff Baker: 206-464-8286 or gbaker@seattletimes.com.

On Twitter @gbakermariners