SEATTLE - The Twins fell to a season-worst 20 games under .500 on Sunday, and this is threatening to get ugly again -- as in, 2011 ugly. As in, get ready for a whole new discussion about avoiding 100 losses.

From the All-Star break through Aug. 7, they scored more runs (143) than any other team in the majors. Since then, the offense has all but disappeared, and they're having trouble masking their pitching problems.

On Sunday, the Mariners withstood six innings of Samuel Deduno's rope-a-dope punches and pulled away for a 5-1 victory at Safeco Field, completing a three-game sweep.

The Twins went 0-for-10 with runners in scoring position for the day and 3-for-38 for the series.

"A bad series here," manager Ron Gardenhire said. "We scored six runs in three days. That's not good enough. They pitched well, but we sure missed out on a lot of opportunities."

Since Aug. 8, the Twins are 1-9, and their offense ranks second-to-last in the majors over that stretch with 33 runs scored.

"We've got to try to figure it out when we get to Oakland [on Monday]," Joe Mauer said. "It's definitely not acceptable."

That's the scary part. The Athletics have one of the best pitching staffs in the majors, including Monday starter Brandon McCarthy, who is 6-2 with a 2.33 ERA in his past 10 outings.

After leaving Oakland, the Twins will fly to Texas for a four-game series against the two-time defending American League champions.

The Twins are 50-70. At this point last year, they were 53-67. Of course, the 2011 squad wobbled toward the finish with injuries to Mauer, Justin Morneau and Denard Span. They needed a walk-off victory on the season's final night to finish 63-99.

"Last year, everybody was so banged up as we worked towards the end, it was completely different," Morneau said. "It's a different feel this year. Obviously, it's the dog days, the tough part of the season, but everybody's still busting their tails. That's why it's so frustrating. Everybody's available, and you're not getting the results you want."

On Aug. 8, the Twins had a chance to sweep Cleveland, which would have pulled them even with the Indians for third place in the division. Now, the Twins are languishing in last place again.

"We look up at those teams in front of us, and we don't feel like those teams are better than us," Morneau said. "I think that's tough when you're looking up at Cleveland and Kansas City. Detroit and Chicago are obviously having good years, but we don't feel like we're too far off from them."

Sunday's loss could have been much worse, but Deduno (4-1) held the Mariners to two runs over six innings, despite walking six batters and hitting another.

Seattle scored three runs off Jeff Gray in the seventh, but he wouldn't have been in the game if the Twins could have converted more of their earlier scoring chances.

"I think one of the biggest things you see is how important Denard Span is in our lineup," Morneau said after the team fell to 1-5 with Span out because of a sore clavicle. "He's the guy setting the tone. Obviously, Ben Revere's capable of doing that job, but Denard's been our leadoff hitter for a while."

Span didn't appear close to returning Sunday, so the Twins try to turn things around without him. They are on pace to finish 67-95, and that could get worse before it gets better.

Joe Christensen •