SEATTLE -- In need of a spark for their struggling offense, the Seattle Mariners took a significant step to try to avoid completely falling out of the American League West race.

Seattle acquired slugger Mark Trumbo from the Arizona Diamondbacks on Wednesday as part of a six-player trade, pulling the trigger on the first major trade of the season with the underachieving Mariners already facing a near double-digit deficit in their division and coming off a fifth straight loss.

The Mariners announced the trade after a 3- 1 loss to the New York Yankees in which the lack of pop at the plate was on display again. Seattle entered Wednesday with the lowest batting average and second-worst on-base percentage in the AL.

"You look at where we were offensively, and we're not doing exactly what I thought we would do or most people thought we would do, and Trumbo is a guy that brings an awful lot to the table," Seattle general manager Jack Zduriencik said. "He's a big power hitter that will bat somewhere in the middle of our lineup. Thought he would be really good insurance for the ballclub."

Arizona also sent left-handed pitcher Vidal Nuno to the Mariners, while catcher Welington Castillo, right-handed reliever Dominic Leone and minor leaguers Gabby Guerrero and Jack Reinheimer are going to the Diamondbacks.

Nuno will start in Seattle's bullpen, Zduriencik said, while Castillo provides stability at catcher for the Diamondbacks after Tuffy Gosewisch was lost for the season to an ACL tear. The trade also makes room for third baseman Jake Lamb's return from the disabled list with Yasmany Tomas playing more in the outfield.

Castillo was acquired by Seattle on May 19 to be an offensive upgrade as the Mariners' backup catcher. But Arizona has a dire catching situation with Gosewisch done for the season. Jordan Pacheco and Jarrod Saltalamacchia have handled the catching duties since Gosewisch was injured last week.

"Not that Salty's not the answer, but we really wanted to address that area. Lamb's going to be coming off the disabled list pretty soon, so it's just going to create more of a logjam for us," Arizona GM Dave Stewart said. "With Yasmany swinging the bat as well as he is, it created a situation where we really needed to open up some space for him."

Arizona also realizes some cost savings with the deal. Trumbo is making $6.9 million this season and could be on track to earn about $10 million through salary arbitration in 2016.

Will Trumbo Help Mariners? Mark Trumbo has hit for power throughout his career, but that was already a Mariners strength this season. Seattle ranks 28th in the league in runs per game due in large part to a weak on-base percentage, something Trumbo doesn't address. Mariners This Season MLB Rank HR 62 5th OBP .297* 27th Runs/Game 3.6 28th K pct. 22.3 28th *Trumbo: .299 OBP (129th in MLB) -- ESPN Stats & Information

Trumbo is hitting .259 with nine home runs and 23 RBIs for the Diamondbacks, playing 40 of his 46 games in right field with one start at first base. He gives the Mariners a right-handed power bat to complement Nelson Cruz and help balance their lefty-heavy lineup.

Trumbo's addition also should provide an opportunity for Seattle to use Cruz at designated hitter more often.

Trumbo did not play in Arizona's 9-8 win over Atlanta on Wednesday and stood stunned at his locker after being told of the deal.

"I knew it was a possibility so I guess it's not something that catches me completely off guard but it's a bit of a shock," Trumbo said. "You get comfortable somewhere and you develop a bit of a rapport and you have great teammates and you're removed from that situation and you know, it's tough."

Seattle was expected to be a contender in the AL West but is 24-29 after starting an 11-game homestand 1-6. The Mariners have been over .500 for one day all season, and while the problem in the first couple of weeks was starting pitching, the problems of the past month have been more at the plate.

Five of Seattle's regular starters are hitting under .250, including Robinson Cano, who is 4-for-23 on the homestand and hitting .211 since May 13. Cano has a .627 OPS, while catcher Mike Zunino (.613) and outfielders Austin Jackson (.665) and Dustin Ackley (.546) also have been disappointing.

Mark Trumbo described Wednesday's trade as "a bit of a shock." Christian Petersen/Getty Images

Trumbo doesn't solve all of Seattle's offensive problems, but he does lengthen the lineup and give manager Lloyd McClendon a few more options.

"I think there's probably an exclamation point here doing the deal now and not waiting and trying to get some immediate help now to add to this lineup," Zduriencik said.

Nuno was a starter at Triple-A this season and made three relief appearances with the Diamondbacks. Most of his time in the majors has been as a starter.

"To bring a pitcher like him who has started in the past, who's also been in the bullpen, who is versatile kid, tough, has five years of control, we think it's an asset to the organization," Zduriencik said.

ESPN.com's Jerry Crasnick and The Associated Press contributed to this report.