MIAMI — The Miami Marlins' highly touted bullpen has been a bust, and so the dismantling began Thursday.

A seller once again as the non-waiver trade deadline approaches, Miami sent right-hander David Phelps to the Seattle Mariners for four prospects, including highly regarded outfielder Brayan Hernandez.

Also acquired by the Marlins to shore up their weak farm system were right-handed pitching prospects Pablo Lopez, Brandon Miller and Lukas Schiraldi.

Phelps is 2-4 with a 3.45 ERA in 44 games and 47 innings this season, all in relief. The bullpen was expected to be a strength, but it faltered and the Marlins appear destined to miss the playoffs for the 14th year in a row, the longest such drought in the NL.

As a result, Miami is shedding payroll for prospects.

"This is something we hoped we could have avoided," president of baseball operations Michael Hill said. "As we look to the rest of the season, we wanted to see if we could get value for certain assets. Relief pitching brings a lot of value."

Closer A.J. Ramos is also a target of trade talk.

"It has been very comparable to the David Phelps market," Hill said. "As teams look to solidify their bullpen, A.J. should be someone they have interest in."

The Mariners shored up their bullpen at the start of a 10-game homestand that begins against the New York Yankees and leads into the trade deadline. After a 5-1 trip following the All-Star break, the Mariners are 48-48 and 1 1/2 games behind the Yankees in the AL wild-card standings.

Phelps is a versatile six-year veteran with 64 career starts.

"He becomes perhaps the most versatile reliever we have now in some ways," Seattle general manager Jerry Dipoto said. "He has the physical ability to go more than one inning, because he has the ability to face the lefts and the rights and he has the physical stuff to get strikeouts in a critical situation either with runners on base or just getting through toward the end of the game."

Phelps will join a bullpen that was overworked during the first half of the season as the Mariners dealt with major injuries to the rotation. They're fifth in the AL in innings pitched by the bullpen.

Seattle has solidified its eighth- and ninth-inning roles, with Nick Vincent typically the setup man for closer Edwin Diaz, but getting to that point has been a struggle at times. Phelps should provide manager Scott Servais more options to bridge the late innings.

Phelps also fits a desire by Dipoto to acquire players who aren't short-term rentals. Phelps will be under Seattle's control through the 2018 season.

"That's been the primary focus, is finding players that are sustainable, that can be a part of what we're doing," Dipoto said. "We still have a need for David Phelps in 2018."

Hernandez, a 19-year-old Venezuelan, is batting .259 in 31 games in the minors this year. He'll be assigned to the Marlins' short-season Class A affiliate in Batavia, New York.

"We got four players we really like," Hill said, "and they'll help create more depth in our minor league system."

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AP Sports Writer Tim Booth in Seattle contributed to this report.

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