OAKLAND -- Whether it's the toll of innings adding up for Marco Gonzales or just an August slump, the young Mariners lefty took his third straight loss on Monday as the A's held on for a 7-6 win in the opener of a key three-game series at the Coliseum between American League playoff challengers.
Gonzales, the Mariners' most-consistent starter through the season's first four months, allowed four runs on eight hits over five innings in falling to 12-8 with a 3.91 ERA. He's 0-3 with a 7.94 ERA in three starts this month after going 5-0 with a 1.57 ERA over five outings in July.
The 26-year-old totaled 126 1/3 innings in 2017 between the Major and Minor Leagues after missing all of '16 recovering from Tommy John surgery. He's already at 142 2/3 this season -- second on the Mariners behind Mike Leake's 146 2/3 -- with seven weeks left in the regular season.
Manager Scott Servais acknowledged Gonzales hasn't been as sharp of late and the workload is a concern, but the lefty will get an extra day of rest before his next start because Seattle has an off-day Thursday after playing 20 straight days.
"It's a good question," Servais said. "He has grinded through a number of outstanding outings for us and is at kind of a new level for him with the innings pitched. I think an extra day will certainly help him next time out."

Gonzales wasn't using the workland as an excuse, however.
"No, I feel confident in where I'm at and how my body feels," he said.
The loss snapped the Mariners' four-game winning streak following their sweep in Houston, dropping them to 69-51, 4 1/2 games back of the Astros for the AL West lead and 2 1/2 behind the A's for the AL's No. 2 Wild Card spot.
The two AL West rivals will face each other nine more times in the final 42 games of the season. Seattle is 6-4 against the A's this year, but Oakland is on a roll, having gone 37-12 since June 15, tied with Boston for the best record in the Majors. Seattle is 24-26 in that same span.

A's starter Sean Manaea (11-8, 3.44 ERA) allowed just just five hits and two runs in 7 2/3 innings, but the Mariners -- down, 7-1, heading into the eighth -- went to work against the Oakland bullpen.
Jean Segura went 4-for-5 with an RBI and Mitch Haniger was 3-for-5 with a double and two RBIs as Seattle scored five runs in the eighth and ninth. Haniger, who scored twice, is hitting .545 (12-for-22) with six doubles in five games since moving into the leadoff spot.
The Mariners forced the A's to bring in closer Blake Treinen after drawing three straight walks off Jeurys Familia to load the bases with no outs in a 7-3 game in the ninth. Treinen unleashed a wild pitch to allow one run to score, and Haniger laced a two-run single to cut the lead to 7-6 before Treinen struck out Nelson Cruz to strand a pair of runners and record his 31st save.
"That bullpen is really good," said Segura. "We came here to win, but they are a good team, too. They've been playing well, like us, and they have a good bullpen. When you're down by six and make it close and get Treinen in the game, it makes you feel good because to come back on a bullpen like that, we gave it a good finish."

The Mariners fell to 30-15 in one-run games, not quite able to finish off an A's team that is 49-0 when leading after seven innings, the only MLB team yet to lose in that situation.
"We had the right guys up there and had some great at-bats in the ninth against their back-end guys," said Servais. "Cruz had a great swing at that first pitch, and it was so close. We were right there, and it would have been a heck of a comeback. Our guys continue to fight."
Oakland third baseman Matt Chapman hit three doubles -- tying a franchise single-game record -- and scored three runs, while Jed Lowrie was 3-for-5 with two doubles and four RBIs, but the A's were just happy to hang on at the end.
"We've done that a few times before," A's manager Bob Melvin said. "The other end of it doesn't feel so great. But when you have Blake Treinen and what he's done, you're confident. Haniger's just been a pain in everybody's side to this point. They have a deep lineup, and obviously with their record in close games, there's no quit in them as well."
MOMENTS THAT MATTERED
The Mariners got on the board against Manaea in the fourth when they bunched two hits and a walk together to make it a 4-1 game on a bloop single by Kyle Seager. But the A's prevented things from getting a lot more interesting when Chapman made an outstanding diving stop to his left on a hard grounder to third by Segura on what would have been an RBI single after Haniger's leadoff double.
"Every time you hit the ball, you think it's going to find a hole," Segura said. "I thought that was going to be a hit, but he's a really good third baseman. For me, he's one of the best third baseman I've seen."

SOUND SMART
The Mariners were 23-17 when Robinson Cano was suspended on May 15. In the 80 games he's been out, they went 46-34 -- for the exact same winning percentage over twice as many games. Cano will rejoin the Mariners on Tuesday.
• Cano set to rejoin Mariners

HE SAID IT
"I have expectations for executing pitches, so if there's any frustration at all, that's where it comes from. Right now, I'm just confident in the process of bouncing back from these starts. I'll take it as an opportunity to learn from it and hopefully come out and be better the next time." -- Gonzales
UP NEXT
James Paxton (10-5, 3.63 ERA) will look to continue his run of success against the A's in Tuesday's 7:05 p.m. PT game at the Coliseum. The big lefty is 3-0 with a 3.32 ERA in seven career outings against the A's and struck out a career-high 16 batters in seven scoreless innings on May 2 in his only meeting with them this year. Oakland counters with right-hander Mike Fiers (7-6, 3.40), making his second start since being acquired from the Tigers.