SEATTLE -- Let the arms race begin.
At least, the race for relievers.
The Yankees acquired right-handed relievers David Robertson and Tommy Kahnle, as well as two-time All-Star third baseman Todd Frazier, on Tuesday night from the Chicago White Sox in exchange for reliever Tyler Clippard and three prospects.
The Mariners, who are chasing the Yankees for an American League wild-card berth, countered Thursday by getting reliever David Phelps from the Miami Marlins for four prospects: outfielder Brayan Hernandez and right-handed pitchers Pablo Lopez, Brandon Miller and Lukas Schiraldi.
"David's really been tested in the bullpen and as a reliever," Mariners general manager Jerry Dipoto said. "He's been under-the-radar good."
Phelps, a 30-year-old right-hander, is scheduled to join the Mariners for the Friday game. He was 2-4 with a 3.45 ERA in 44 appearances for Miami, with 51 strikeouts in 47 innings. His 18 holds were tied for second in the National League.
Phelps, who made his major league debut with the Yankees in 2012, is in his first full season as a reliever after bouncing between the rotation and a long-relief role for most of his first five seasons.
"It's nice to have another arm on the way," Mariners manager Scott Servais said. "He can pitch anywhere from the sixth, seventh or eighth inning."
The Yankees and Mariners are still in the market for starting pitching.
Seattle expected left-hander Drew Smyly would return by the All-Star break, but he is going to miss the remainder of the season and perhaps most of 2018 after undergoing Tommy John surgery. Right-hander Hisashi Iwakuma has been on the disabled list since May 10 with inflammation in his pitching shoulder, and it is unclear when, or whether, he will return after setbacks in his rehabilitation.
The Yankees recently lost right-hander Michael Pineda, a former Mariner who has a partial ligament tear in his pitching elbow and might undergo surgery.
"We wanted to be careful buyers and we wanted to improve areas on the club," Yankees general manager Brian Cashman told NJ.com. "The biggest areas would be with the Michael Pineda injury if we can find a spot in the rotation as well as improve the bullpen. We do believe clearly that this (trade) adds some significant weapons to the high-caliber pieces that we already possess in the bullpen, and hopefully it plays out that way as we move forward."
Dipoto said he has talked with "every team in the league" about acquiring a starter.
"The demand exceeds the supply," Dipoto said. "The market for (starting) pitching is high. We've got to be realistic about what we can offer."
With that in mind, the Mariners announced Thursday that veteran right-hander Yovani Gallardo would return to the rotation and start the series finale Sunday. Gallardo was 3-7 with a 6.30 ERA in 14 starts before being banished to the bullpen a month ago.
Dipoto was asked whether the Mariners would consider a "rental" player who is signed only through this season.
"I would if the rental costs much less," he said. "In theory, it should be toward the end of the month (at the trading deadline)."
But Dipoto admitted that theory might be skewed this season, with nearly every AL club still in the wild-card race.
"You're still going to pay a premium for a short-term buy," he said.
The Mariners are scheduled to send rookie right-hander Andrew Moore (1-1, 5.25 ERA) to the mound Friday to make his first appearance against the Yankees.
New York plans to pitch veteran left-hander CC Sabathia (8-3, 3.54), who is 13-6 with a 2.64 ERA in 26 career starts against the Mariners.