Everything was smooth sailing for Justin Dunn in Thursday’s 6-3 win against the Giants, until it wasn’t. The Mariners’ right-hander retired each of his first seven batters, including impressive strikeouts against Tommy La Stella and Evan Longoria. Then, before he could catch his breath, Dunn walked the bases loaded, couldn't get out of the third inning and was charged three runs.

“Honestly, I just got in my own head,” Dunn said. “We tried to overcorrect the miss. That third inning was just 2019 Justin. That's the simplest way to say it. I've got to flush it. Obviously, I'm not happy with it, but I know that's not who I am and who I'm going to be this season.”

These are the types of jams that Dunn wants -- and needs -- to clear to hang on to the sixth and final spot in the Mariners’ starting rotation. At times this spring, Dunn has had some of the best stuff on the staff: a fastball that he’s dialed up to 97 mph, quality breaking pitches that have depth and movement and a blossoming changeup. He’s said that this spring has been so refreshing because he feels he has all his weapons again, and he reiterated that on Thursday.

But when command eludes the 25-year-old, the issue becomes more pronounced more quickly. Dunn has walked six in 7 2/3 innings this spring, and last season, his 15.2 percent walk rate was second-highest among 111 qualified pitchers.

“I can't walk three guys,” said Dunn, who came back to strike out Mike Yastrzemski immediately after then threw a wild pitch that allowed a run and gave up a double to Donavan Solano to end his night.

“After [Mariners pitching coach Pete Woodworth] kind of slowed me down and reminded me to get away from mechanics and just go back to competing and trusting my stuff. My line felt better, and I can take those last two hitters into next week. But obviously, not happy about it, but a lot of positives to take from it at the same time.”

There were certainly positives from Thursday, notably the impressive punchouts of La Stella -- whose 5.2 percent strikeout rate last year was the Majors’ best by a long shot -- and Longoria, who froze on an impressive breaking ball. His competitor for the open rotation spot, Nick Margevicius, put up three scoreless innings with five strikeouts and just three hits allowed.

“I’m taking the learning lesson,” Dunn said. “I'd rather have it happen now. [I need] to be able to speed that up and not have three walks and be able to get the next hitter right after the first one.”

Visa issues delaying Paxton’s debut
James Paxton’s delay has been due to work visa issues, general manager Jerry Dipoto said on MLB Network Radio. The Canadian has been permitted to throw on backfields because those events are not related to gate revenue.

But the delay should be ending soon. Servais said that Big Maple will make his next scheduled turn through the rotation on Saturday against the Rangers in Surprise or Sunday against the Brewers in Maryvale.

Dipoto reiterated to Chris Russo on MLB Network on Wednesday that Paxton is healthy, and that he anticipates the left-hander to pitch in one of the Mariners’ first three games of the regular season against the Giants.

Injury updates
• Reliever Andres Muñoz has experienced a setback in his rehab from Tommy John surgery and has not been throwing much over the past few weeks. Munoz, who underwent the procedure last March, was eyeing a return in the May-to-June range.

• Reliever Domingo Tapia has begun his throwing program after being sidelined since straining his right oblique against the White Sox on March 5. Tapia had been contending for one of the lower-leverage spots in the bullpen, but his status for Opening Day is unlikely, given the need to ramp back up and that recoveries for oblique injuries can be a matter of weeks.

• Second baseman Shed Long Jr. (right shin) has began running on Peoria Sports Complex backfields and is “moving better,” per Servais. Long has been taking batting practice, but that hasn’t been the root cause of his pain; it’s the cutting and quick movements that he executes in the field. That’s the primary reason that the 25-year-old hasn’t been installed in a Cactus game.

'B' game set for Saturday
For the third time this spring, Yusei Kikuchi will square off against the Indians, but this time, it will be in a five-inning “B” game on a backfield at Goodyear Ballpark. The Mariners had been trying to coordinate such games all spring in order to stretch out the 42 arms that they initially invited to camp, but they’ve have had little luck due to the dearth of options among the other West Valley clubs.

Servais said that a handful of the club’s younger position players will play in the “B” game.