Mariners 11
Red Sox 4

SEATTLE — The Red Sox are still in the first place in the American League East and they have the most victories in baseball. But they are wobbling to a point where general manager Ben Cherington may have to act.

Another poor performance by Jon Lester and shaky work by the bullpen led to an 11-4 loss against the Seattle Mariners Monday night at Safeco Field.

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The Red Sox are 1-3 on a West Coast road trip that has six games remaining. They have dropped three straight for the first time since May 11-14.

The day started with the news that lefthander Andrew Miller, a key member of the bullpen, needs season-ending surgery on his left foot.

Then the Sox learned that center fielder Jacoby Ellsbury couldn’t play against Seattle because of a sore left wrist. Right fielder Shane Victorino missed his second consecutive game with a tight left hamstring. That left manager John Farrell with little choice but to put Daniel Nava in center field.

Nava’s professional experience at the position consisted of 13 innings in the minor leagues.

Lester could have softened those blows with a good start. But he lasted only five-plus innings, giving up five runs on nine hits.

Lester (8-5) has two quality starts in his last 10 and an earned run average of 4.60.

Rookies Alex Wilson and Jose De La Torre were hit hard, too. Nava committed an error and misjudged several balls.

Seattle has one of the worst offenses in the league. But the bottom third of that weak lineup — Justin Smoak, Mike Zunino, and Michael Saunders — was 7 for 12 with four doubles, six RBIs, three walks, and five runs.

Raul Ibanez was 2 for 5 with a home run and two RBIs. Seattle, which has won five of its last seven games, scored its second most runs this season.

Felix Hernandez (9-4) cruised through seven innings for the win, allowing two runs on six hits. He walked two and struck out six to improve to 7-2 in 13 career starts against the Sox.

Now the Red Sox will send rookie Allen Webster to the mound on Tuesday against All-Star Hisashi Iwakuma. The Sox have scored four runs over their last 21 innings.

Seattle took a 2-0 lead in the fourth inning. It was a rare time when Dustin Pedroia’s hustle hurt the Red Sox.

Kendrys Morales started the inning with a single to left. Kyle Seager followed with a hard ground ball to the right side. Pedroia made a diving attempt to stop the ball but it ticked off his glove and veered toward the foul line.

That enabled Morales to take third. Lester struck out Jason Bay then got ahead of Smoak, 1 and 2. But he left a cutter up in the strike zone that Smoak pulled down the line in left for an RBI double.

Lester walked Zunino to load the bases for Saunders, who walked on five pitches to make it 2-0.

Based on Lester’s body language, he thought umpire Ed Hickox missed three of the pitches. But that didn’t hide the fact that Lester walked two of the worst hitters on the team to force in a run.

Zunino, a rookie, came into the game hitting .200. Saunders was at .207.

Lester squirmed out of further trouble. The inning ended when Nick Franklin hammered a ball to center that Nava tracked down at the wall.

The Red Sox came right back against Hernandez in the top of the fifth inning and tied the game.

Hernandez hit Jose Iglesias with a curveball before rookie Brock Holt singled to right. Iglesias took third and scored on a single by Nava.

Jonny Gomes struck out on a sinker but the ball got past Zunino and Holt scored.

David Ortiz walked with two outs before Hernandez struck out Mike Napoli.

Ibanez started the bottom of the fifth inning with a home run to right field. At 41, Ibanez has 22 home runs before the All-Star break. It’s his most in a season since hitting 34 for the Phillies in 2009.

No player older than 40 has ever had as many home runs before the break than Ibanez.

Lester didn’t get an out in the sixth inning. Smoak and Zunino had singles, which brought Wilson into the game. Saunders crunched a belt-high fastball to center field.

Nava could not catch up to the ball and Smoak scored. When Nava’s throw missed the cutoff man and rolled into the infield, Zunino also scored.

With two outs, Ibanez singled to drive in Saunders.

The game got out of hand in the seventh inning as the Mariners scored four runs on four hits — three of them doubles — against Wilson and De La Torre.

Smoak and Saunders had RBI doubles. Brad Miller added an RBI single and Franklin an RBI double. It was 10-2 at that point.