The Seattle Mariners had a guy in their system in 2009 with some serious offensive promise.

His name? Mike Morse. He came up in 2005 and played bits of the next four seasons in Seattle, but never saw a 2009 big league game with the Mariners. It was in the middle of that season that first-year general manager Jack Zduriencik, feeling the need to get a more balanced defensive player, dipped into Triple-A Tacoma roster.

Just like that, Morse was dealt to the Washington Nationals.

The player the Mariners received in return, outfielder Ryan Langerhans, was never more than a part-time player with Seattle before being traded to the Angels in 2011.

In 2011, Morse had 31 homers and 95 RBIs while hitting .303. He hadn’t had much of an impact in D.C. the year of the trade, but the next three seasons he hit 64 homers and was a major power threat when injuries weren’t keeping him out of the lineup.

And now Morse is a Mariner once more. Seattle, the Oakland A’s and the Washington Nationals executed a three-way trade Wednesday, with the A’s getting catcher John Jaso from the Mariners. The Nationals, who signed free agent slugger Adam LaRoche earlier, let Morse head to the Northwest while getting two minor leaguers and a player to be named later from the A’s.

Morse is the fourth player the Mariners have acquired this off-season with at least one 30-homer season in his past. Given the dearth of power, manager Eric Wedge’s lineup should be packing much more punch.

Or should it? The jury is out on that one. None of the 30-homer seasons came in 2012. Jason Bay, 34, had his last 30-homer season aback in 2009. Kendrys Morales, 29, had his only 30-homer season in 2010. And Raul Ibanez, 40, had his last 30-homer season in 2009.

But Morales and Morse, after overcoming injury issues in 2012, had most of their best production the second half of the season – 14 homers and 40 RBIs in 59 games for Morales after the break for the Angels while Morse came in at 14 homers and 46 RBIs down the stretch.

“I didn’t get to play spring training,” Morse said Wednesday night, referring to a back injury that cost him about 50 games. “When I got back, I had maybe 20 at-bats in rehab (before being pushed into duty). And I still hit .291 with 18 (homers). I feel I can hit the ball out of the Grand Canyon.’’

The Mariners would like to think so. They are banking on it. At 6-foot-5 and 245 pounds, Morse is no longer the shortstop he once was, although he repeatedly lobbied for a chance get some time there, because it’s where he feels the most comfortable. At this point, however, most realists see Morse as a first baseman, a corner outfielder and occasional DH. The Mariners are getting a little packed at that position.

Bay and Ibanez are corner outfielders. Morales is a first baseman/DH. Jesus Montero is a DH when he’s not catching. Michael Saunders can play all three outfield positions, but won’t play center over the now-healthy Franklin Gutierrez. Mike Carp fits the outfield/first base/DH mode. Casper Wells, like Saunders, can play all three outfield spots, but he’s looking at a tough road to playing time this spring.

“This gives us some big pop in the lineup,” Zduriencik said. “We were looking for a banger, and in Michael, I think we got that.’’

As some cost, it should be noted. The Mariners are now desperately in need of a backup catcher, and Zduriencik confirmed that he’s already had talks aimed at filling that gap. Jaso and Montero were going to share the catching chores, and while the Mariners believe they are deep at the position in the minor leagues, particularly with 2012’s No. 1 draft pick Mike Zunino, they need someone with veteran cred.

“In Jaso, we know what he is and what he can do,” Zduriencik said. “He was going to be a part-time player. When you are in position to acquire an every-day guy who can hit the ball hard and hit the ball far, that helps.

“We’re going to be shopping (for a catcher), there’s no doubt. We had some discussions yesterday when it seemed this might happen. We like our catching in our organization (but the club needs help) right at the very top.’’

Based on his past, Morse isn’t a big-time acquisition. Based on the numbers he put up with the Nationals, however, he could turn out to be one.

And he’s up for the challenge. Ibanez, who is a close friend and workout partner in Florida, texted Morse to say “now we can contend; now we’re ready.”

Morse went so far as to thank Zduriencik – the man who traded him away without giving him an at-bat – for bringing him back.

“I’ve grown as a player; I’ve grown as a hitter,” the 30-year-old said. “I’ve put in a lot of hard work, been through rough times and good times. I’m happy, more than that, really excited. It’s great.

“I know there were teams involved (in trying to trade for him) and I knew Seattle was one of them. That’s one of the teams I was hoping for. I was telling Jack that I had unfinished business in Seattle. I never got the chance to prove the player I could be. This is another opportunity for me to show Jack and help this club be the World Series champ (I think) it could be.’’

As part of getting Jaso, the A’s traded a pair of right-handed pitching prospects, A.J. Cole and Blake Treinen, to the Nationals, and still owe them a player.