Triunfel, a 22-year-old rookie, was selected from Triple-A Tacoma on Sept. 4 and had appeared in five games as a defensive replacement prior to Friday.
With the game tied, 2-2, in the fourth, Triunfel hit a high chopper down the left-field line that easily cleared third baseman Michael Young. The double -- Triunfel's second big league hit -- scored Casper Wells from first, giving the young shortstop his first RBI in the Majors.
Triunfel advanced to third on a groundout and then scored his first MLB run with two outs on an error by Young to pad the Mariners lead, 4-2.
"I went out there to just play my game and I'm glad I did it," said Triunfel on his double through interpreter Fernando Alcala. "It feels good because it scored a run and it helped the team win."
Hisashi Iwakuma allowed a home run to David Murphy in the sixth -- a liner that got over the wall in right in a hurry -- to make it 4-3, but the 31-year-old Japanese rookie would not let the Rangers get any closer.
In seven innings of work, Iwakuma scattered eight hits, allowed three runs, struck out four and did not issue a walk. The right-hander improves to 6-4 as a starter and 1-2 with a save against the Rangers.
"He hung in there for seven innings and only gave up three runs," Rangers manager Ron Washington said. "He kept his team in the game, which is the first thing you want a starting pitcher to do."
"He had something on the end of his pitches," Wedge said. "Had a good fastball, some good splitties, good sliders. Again, he's a veteran guy out there. He pitches like an experienced starting pitcher. He executes pitches, he understands different situations and what type of pitch he wants to throw depending on that. I think he does a good job recognizing swings, too."
The Mariners took a 2-0 lead with runs in the second and third. Justin Smoak doubled on a scorching line drive down the left-field line to lead off the second and scored on a nearly identical two-bagger by Wells.
Wells' RBI knock snapped the Mariners' 0-for-22 skid with runners in scoring position, a streak that started in Tuesday's 18-inning marathon against Baltimore.
"We had some tough battles against the Orioles, some long battles, but it's nice to see us come through and get some run," Wells said.
The Mariners added to their lead in the third when Franklin Gutierrez rocketed a triple off the center-field fence and then scampered home on a wild pitch.
The Rangers got the two runs back in the fourth when David Murphy singled home Young and Nelson Cruz.
Miguel Olivo's two-run home run in the eighth padded the Mariners lead, 6-3. The blast to left field also gave the Mariners a home run in 11 consecutive games, which ties their season high. Seattle also hit 11 straight from Aug. 17-28.
The home run gave closer Tom Wilhelmsen some breathing room as the first two batters got aboard in the ninth on a single and an error. The tall righty escaped the jam, though, with a double play and strikeout to end the Mariners' four-game losing streak.
"As we continue to get better, and even obviously some of the tough losses we've had of late, we're for the most part right there," Wedge said. "One play, one at-bat or one pitch away from winning those ballgames."