SEATTLE (AP) -- When Jason Vargas talks about being a complete pitcher, he's talking about staying strong for a complete season.

The Seattle lefty stayed on track to meet his goal of having a solid second half, pitching seven solid innings as the Mariners sent the sloppy Boston Red Sox to their season-worst seventh straight loss, 4-1 Monday.

''I feel like the progression I've made has gotten better. The last few years I've struggled after the All-Star break,'' Vargas said. ''That I haven't had as many struggles is definitely a plus. I'm able to keep making adjustments. I've been able to keep myself together.''

Over the past three seasons, Vargas is 7-18 with a 5.37 ERA in the season half. This year, he is 6-2 with a 3.28 ERA since the All-Star break.

''You look at how much progress he has made just in the time I've been here,'' second-year Mariners manager Eric Wedge said. ''He was strong in his last five, six starts last year and he brought it into this year.''

The Red Sox botched two key plays and fell to 0-7 on their road trip. They've been outscored 58-16 in that span.

''We made the miscues that gave them two runs and that's all she wrote,'' Boston manager Bobby Valentine said.

Vargas (14-9) allowed one run and six hits, walked no one and struck out five. He is the first Mariners pitcher other than Felix Hernandez to win at least 14 games since 2003.

Vargas, who leads the staff in wins, was coming off two sub-par outings in which he gave up a combined 11 runs and 15 hits in 8 2-3 innings.

Tom Wilhelmsen worked the ninth to pick up his 23rd save in 26 opportunities.

The Mariners have won 10 of their last 12 games at Safeco Field.

Clay Buchholz (11-5) took the loss. He went seven innings, giving up three earned runs, six hits while walking one and striking out eight.

Buchholz and the wobbly Boston defense conspired to undo the Red Sox in the Mariners' four-run fourth inning.

Buchholz got in trouble after Franklin Gutierrez beat out an infield single. He then walked Kyle Seager and, on back-to-back pitches, gave up RBI single by John Jaso and Justin Smoak to right that gave Seattle a 2-1 lead.

The Red Sox fell apart after that.

Eric Thames lifted a shallow fly ball to center fielder Jacoby Ellsbury and Jaso tagged up, broke for home and then stopped. Ellsbury's throw, however, bounced away from catcher Ryan Lavarnway, and Jaso restarted and scored.

''I wish they had given me that error,'' Lavarnway said. ''Jacoby is trying to get that guy out. He's doing exactly what he should have and I played it into an in-between hop. I need to go out and smother that ball - absolutely need to keep it in front of me.''

Miguel Olivo singled and Carlos Peguero hit what looked like a double-play grounder to shortstop Jose Iglesias. The ball slipped in Iglesias' hand, missing the force at second, and he threw too late to first for an error that let Smoak score.

The Red Sox scored a two-out run in the first. Dustin Pedroia had a ground-rule double for the 1,000th hit in his sixth full season and Cody Ross singled.

NOTES: Notes: Pedroia has matched his season high with a 14-game hitting streak. He has had three hitting streaks this season of 13 games or more. ... Boston DH David Ortiz has played one game since July 18 because of his two stints on the disabled list for a strained Achilles, but general manager Ben Cherington expects the slugger back before the end of the season. ''That's our hope,'' he said. ... OF Michael Saunders has missed eight on the past nine Mariners' games with a strained right hamstring. Manager Eric Wedge said he is close to returning.