SEATTLE — When Baltimore Orioles outfielder Mark Trumbo steps into the box Monday as the No. 1 seed in the Home Run Derby, it won’t come as a huge surprise. Over his career, Trumbo has developed a reputation for his immense power.

But when he takes the field Tuesday for the All-Star game, more than a few faces might be shocked. After making the game in 2012, Trumbo fell off track. The next two seasons, Trumbo hit in the .230s. The power was still there, but his average fell off. The batting average rebounded in 2015, but his home runs and his slugging percentage were down.

Suddenly, he’s become an All-Star again, and it’s all due to last season’s brief stop with the Seattle Mariners.

You wouldn’t know it by his stats there. In Seattle, Trumbo hit .263/.316/.419, with 13 home runs over 361 plate appearances. It wasn’t a standout performance, but it wasn’t terrible either. Based on those numbers, you wouldn’t think a breakout was coming.

View photos Mark Trumbo is the No. 1 seed in the MLB Home Run Derby. (AP) More

But that’s exactly what happened. While his stay in Seattle was brief, the work he did with Mariners hitting coach Edgar Martinez may be the reason he’s recaptured his All-Star form.

“I made some adjustments last year that I’ve spoke about a few times with Edgar across the way here.” Trumbo says. “He saw a few things in my swing that he thought could be better.

“We worked pretty hard on cleaning it up. And from about July up until now, the numbers have been pretty respectable.”

Pretty respectable is an understatement. Trumbo has been one of the best hitters in baseball this season. Through 87 games, he has a .288/.341/.582 slash line. He leads the majors with 28 home runs. That impressive pop made Trumbo the No. 1 seed in the Home Run Derby.

No matter what stats you use, Trumbo is having the finest season of his career. All three stats in his slash line represent a career-high. As does his 141 wRC+, an advanced stat that measures offensive performance. By wRC+, Trumbo has been the 18th best hitter in baseball.

Changing your swing can be a dangerous thing in baseball. It’s one thing to identify places where you can improve, but successfully executing them during a game is much more difficult. If adjustments don’t take immediately, a player can easily get frustrated and go back to his old ways.

“[Making adjustments to your swing] is a process,” Trumbo says. “None of the changes you make are going to take that quickly. They might click for you right away, but often times it’s going to take a little while. You’re going to have to stick with it. It’s really easy to come up with something conceptually and then abandon it quickly if it doesn’t seem to take.”

Of course, it’s much easier to stay the course when you’re working with Edgar Martinez, one of the best hitters in recent memory.

“When you have somebody who obviously knows what they are talking about that sees something, it’s worth listening to,” Trumbo says.

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View photos Orioles outfielder Mark Trumbo leads the majors with 28 home runs. (Getty Images/Otto Greule Jr.) More

Trumbo wouldn’t get into exactly what he altered, but he feels he’s “more direct to the ball” now, and that leads to “more solid contact and fewer foul balls.” Martinez, however, outlined some of the things he worked on with Trumbo in an article by Ryan Divish of the Seattle Times.

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