SEATTLE -- Seattle starter Nathan Karns, who hadn't been on the losing end of a decision since the opening week of the season, knew it was only a matter of time before the Mariners' offense picked him up. Trailing 2-0 after five innings, Karns wasn't too concerned.

And once the bats got going, Karns had more than enough to earn his fifth consecutive winning decision in a 9-2 victory over the San Diego Padres on Monday afternoon at Safeco Field.

"We haven't had that much success (as a starting rotation) lately, but our offense has been producing," Karns said. "I felt like as long as I kept it close, we have a really special offense here, and they showed it today."

Kyle Seager and Dae-Ho Lee each hit home runs, accounting for five runs as the Seattle Mariners (29-21) snapped a three-game losing streak.

Seager gave the Mariners their first lead, at 4-2, with a two-out, two-run homer in the sixth. Seattle scored four runs in the inning to rally from a 2-0 deficit. Designated hitter Adam Lind had a two-run single with the bases loaded in the eighth, then Lee piled it on with a three-run shot for a 9-2 Mariners lead.

"It just kind of got away from us in the sixth," San Diego manager Andy Green said after the Padres (20-32) lost their third in a row.

Seattle's Karns (5-1) allowed two runs off eight hits over 6 2/3 innings to extend his winning streak to five consecutive decisions. His last defeat came on April 9 in his first start as a Mariner.

Padres starter Andrew Cashner (2-5) allowed four runs -- three earned -- off six hits over 6 1/3 innings.

San Diego reliever Brandon Maurer, formerly a Seattle starter whom the Mariners converted into a relief role, endured most of the damage in his one-third inning of work. Maurer came on in the eighth and allowed five runs off three hits, including the Lee home run.

"It's tough to swallow at the end of the day because (Cashner) was really good," Green said. "Those (first) five innings were as good a five innings as he's pitched all year."

Lee, playing in the same lineup as platoon mate Lind for only the third time this season, went 2-for-4 with his seventh home run of the season.

San Diego designated hitter Christian Bethancourt gave the Padres a 1-0 lead with an RBI single in the second inning. Bethancourt's one-out single up the middle scored Melvin Upton Jr., who had singled, stole second base and moved to third on a groundout.

The Padres added another run in the sixth, when first baseman Brett Wallace looped an RBI double down the left-field line with two outs to put San Diego ahead 2-0.

Matt Kemp led off the inning with a double and moved to third on a double-play groundout. Wallace hit a fly ball down the line, and Seattle left fielder Seth Smith ran the ball down near the wall but had it bounce off his glove, easily scoring Kemp from third.

Smith, who was not charged with an error on the play, made up for the drop with an RBI double in the bottom of the inning. Smith's double to left-center scored Norichika Aoki from first base, then Smith scored on a Nelson Cruz single up the middle to tie the score at 2 in the sixth.

Seager followed with his ninth home run of the season.

The rally started when Aoki reached first base on a catcher's interference call that went against San Diego's Derek Norris. Aoki's bat clipped Norris's glove on a third-strike swing that resulted in the free pass.

"Fortunately, we got a break with the catcher's interference, then Seth and Nellie (Cruz) got big hits," Seager said, "and I was able to feed off that."

Seattle broke it open in the eighth. The Mariners loaded the bases with one out before Lind reached out and poked a 1-2 pitch up the middle for a two-run single, putting Seattle ahead 6-2. Lee's seventh home run of the season, and his fourth against right-handed pitching, gave the Mariners a 9-2 lead.

"(Maurer) does a lot of fastballs and sliders," Lee said through an interpreter, "so I was waiting for the fastball."

NOTES: Padres starter Andrew Cashner was making his second start since being activated from the 15-day disabled list. ... San Diego closer Fernando Rodney was designated for assignment, and subsequently released, by the Mariners last season. The veteran reliever has turned it around this year, with a 0.00 ERA heading into Monday. ... The Mariners had 1B Dae-Ho Lee and 1B Adam Lind in the lineup together for only the third time this season. Lee and Lind typically platoon, but Seattle used Lind as a designated hitter Monday while leaving the right-handed Lee against righty starter Cashner. ... The win gave Seattle home record of 11-14. The Mariners are 18-7 on the road. ... The Padres and Mariners officially wrap up a two-game series at Safeco Field on Tuesday, although they'll both be back on the field to meet twice more in San Diego on Wednesday and Thursday.