SEATTLE — Most games this season, a Red Sox starter is celebrating if he goes eight innings and gives up three runs. For Rick Porcello, it wasn’t remotely good enough on Wednesday night.

The West Coast doldrums continued for the Red Sox in a 3-1 loss against the Seattle Mariners.

Hisashi Iwakuma and two relievers held the Sox to seven hits, all singles. The Sox are 3-4 on their road trip, having scored only 21 runs. They are hitting .211 in the seven games, 6 of 41 (.146) with runners in scoring position.

The Sox have lost nine of 13 and at 58-48 are three games out of first place in the American League East. They also have fallen into third place in the wild-card race.

Rookie Andrew Benintendi was 2 for 3, collecting his first major league hits.

Rick Porcello (14-3) allowed three solo home runs to take his first loss since May 17.

The Sox finish the series here on Thursday with Drew Pomeranz on the mound. Then come three games against the Dodgers in Los Angeles.

Trailing, 3-0, the Sox tried to rally in the ninth against new Seattle closer Edwin Diaz.

Jackie Bradley Jr. singled with one out before Aaron Hill was hit by a slider. A wild pitch moved the runners up and Bradley scored when Travis Shaw grounded to second base.

Sandy Leon could not extend the game, grounding into the shift on the right side with Benintendi on deck.

Seattle took a no-doubt-about-it lead in the second inning when Nelson Cruz homered into the upper deck in left field.

Porcello kept a fastball inside but Cruz pulled it 441 feet for his 27th homer of the season.

Iwakuma struck out four of the first five batters he faced before Hill singled with two outs in the second inning. Shaw, starting at first base in place of an injured Hanley Ramirez, popped to second.

With one out in the third inning, Benintendi stayed with a low splitter and lined it the other way for his first major league hit. The Sox made sure to retrieve the ball for the 22-year-old.

Brock Holt singled with two outs but Xander Bogaerts fouled out to end the inning.

Porcello started the sixth inning having retired 11 straight. That ended when Mike Zunino hammered a fastball to straightaway center for his fifth home run, the second in as many nights.

The Mariners had another solo homer in the seventh inning when Adam Lind connected on a changeup over the middle and drove it out to right field. It was his 14th of the season.

Benintendi collected his second hit in the eighth inning, a broken-bat single to right field. That knocked Iwakuma out of the game after 97 pitches.

Facing Drew Storen, Mookie Betts singled to center field and the Sox had their first runner in scoring position.

Holt popped to shortstop. Bogaerts then sent a fly ball deep to left field. As the many Red Sox fans in the crowd of 24,494 cheered, the ball died on the warning track and was caught by Norichika Aoki.

Iwakuma came into the game with a career 8.59 earned run average in five career starts against the Red Sox. Over 22 innings, he had allowed 21 earned runs on 39 hits, five of them home runs.

Iwakuma also had pitched poorly his last time out, lasting only three innings against the Chicago Cubs on Friday. He gave up five runs on eight hits in that game.

On Wednesday, he worked through the Red Sox lineup with ease. He scattered five hits and struck out seven without a walk.

Peter Abraham can be reached at pabraham@globe.com. Follow him on Twitter @PeteAbe.