ARLINGTON -- The Mariners had a Texas-sized problem on their hands from the get-go on Friday night, with the start to their most critical series of the season beginning on the toughest possible note.

Seattle entered the fifth inning at Globe Life Field hitless against Rangers starter Dane Dunning and exited the frame in an eight-run deficit, a hole that proved too deep to dig out of in an 8-5 loss to the club that they’re chasing in both the American League West and the AL Wild Card race.

• Games remaining (9): at TEX (2), vs. HOU (3), vs. TEX (4)
• Standings update: The Mariners (84-69) fell one game behind the Rangers (85-68) for first place in the AL West. They are a half-game back of second-place Houston (85-69). The Astros also hold the third and final AL Wild Card spot, making the Mariners the first team on the outside looking in.
• Tiebreakers: Win vs. Houston (8-2); lose vs. Texas (1-6, though the Mariners' season series vs. the Rangers is still undecided, Texas would win the tiebreaker in any scenario in which the clubs could end up tied); likely win vs. Toronto (3-3, tiebreaker based on intradivision record).

The Mariners showed offensive life with four runs in the sixth, when they sent the tying run to the plate, and the ninth, when they plated another and had the winning run in the batter’s box. But they ultimately fell short in those sequences -- both with the bases loaded -- capped by Ty France’s game-ending groundout that ended the first baseman’s 0-for-5 night.

“These two teams are going to swing at each other here for the next week and a half,” Mariners manager Scott Servais said. “I mean, that's just what's going to happen. The games are going to go back and forth, and you're never out of the game.”

On one hand, the Mariners battled back and proved that despite this stinging start, there will be opportunities to strike against the Rangers’ leaky bullpen, which carries a 4.88 ERA and has blown 32 saves, tied for MLB’s most.

On the other, to do so effectively, Seattle will need to be far more productive earlier in its final six games against division rival Texas, which took sole possession of first place after Houston lost to Kansas City. The Mariners got virtually nothing going against Dunning, who threw a season-high 46% sliders and landed most at the bottom of the zone, as 10 of his 16 outs were on the ground.

Seattle fell into its big deficit after Bryce Miller surrendered homers to Corey Seager and Evan Carter in the first two frames, a solo shot and three-run blast, respectively, and both on the first pitch. Miller threw 17 first-pitch strikes to his 20 batters, but an aggressive Rangers offense capitalized.

Seager’s shot came on a fastball that was middle-in, while Carter’s came via an offspeed pitch over the heart of the plate, the first changeup that Miller threw all game.

“I'll take a solo home run all day,” Miller said. “But it's the three-run home runs that we have to limit. ... I could have made a better pitch [to Carter]. If I did it again, I wouldn't throw the changeup. But I threw a lot of strikes today, but just really those two pitches, they got me.”

Miller settled in and retired eight in a row entering the fifth, but a leadoff walk to Carter coupled with a stolen base and a single to Seager ended the rookie’s night. From there, Tayler Saucedo induced a weak grounder to France, but the Mariners were unable to turn the double play and the inning continued.

Saucedo then surrendered a single and consecutive walks -- one to load the bases then another to bring home a run -- after which Servais turned to Trent Thornton, who gave up an RBI knock to Mitch Garver to open the floodgates. To that point, the Mariners had been outscored at Globe Life Field 38-9 this season.

“I hate walking people,” Miller said. “I walk a guy in the fifth and he comes around to score. I've just got to be better.”

Seattle rallied with a three-run homer from Cal Raleigh -- his 30th of the year, setting a franchise record among catchers -- and a bases-loaded walk from Josh Rojas, which flipped the lineup to J.P. Crawford. But Seattle’s shortstop, who was 9-for-13 with 20 RBIs with the bases loaded entering the at-bat, grounded out to halt the rally.

One game down, nine to go in this stretch that will define the fate of Seattle's season.

All is not lost. Far from it, actually -- especially as the Astros also fell. But it was hardly the start that the Mariners had hoped for.

The more pressing concern is that Seattle’s September stumble has created alarm. The Mariners are 8-12 this month, but more notably, they fell to 2-9 against teams above .500 following series against the Reds, Rays and Dodgers, who swept Seattle at T-Mobile Park last weekend. For the season, the Mariners are 31-42 against winning teams and 53-27 against clubs under .500 following their three-game sweep of 107-loss Oakland this week.

Winning teams will await in the postseason -- but first, the Mariners have to get there.