SEATTLE -- The hard-hit grounder was right at Luke Raley but it scorched under the first baseman’s glove and set off a string off frustrating sequences in the eighth inning on Thursday night that sunk the Mariners to another gut-punch loss, this one a 5-4 defeat vs. the Rangers at T-Mobile Park.

Raley was charged an error on the play, which allowed Josh Smith to reach and extend Texas’ slow-building but eventually suffocating rally. The plate appearance was just after Marcus Semien crushed a homer off Collin Snider to make it a one-run game. Then, with Smith aboard, Snider surrendered a deep double to Wyatt Langford that sent Seattle to red alert.

But it didn’t stop there.

A groundout from Adolis García allowed the speedy Smith to score easily from third base, tie the game and spoil Seattle’s three-run lead from earlier. It also prompted a pitching change to Tayler Saucedo, who served up another hard-hit infield chopper -- this one at Jorge Polanco and one that the second baseman couldn’t field cleanly, allowing the game-winning run to score.

The ticketed 22,212 on hand were in just as much disbelief as the home dugout, which was occupied by a group that made its already uphill climb to October even more steep with another deflating defeat.

“It led to a big inning,” Raley said of the error, “but it wasn't for a lot of effort. I mean, I tried to make the best read I could on the ball and it kicked in a way I didn't think it was going to kick -- and what happened, happened.”

The Mariners (74-73) fell to 4 1/2 games back in the American League West after the Astros won earlier, and 4 1/2 games back of the final AL Wild Card spot, tied with Boston and with Detroit in between.

With six innings of one-run ball from Bryce Miller, and considering how Seattle’s offense pounced in their first frame against the Rangers’ leaky bullpen, it looked like the Mariners would reach the finish line after breaking a 1-1 tie with a three-spot in the fifth.

They capitalized on a quickly elevated workload from Kumar Rocker, who was making his much anticipated MLB debut, and tied the game when Justin Turner crushed a full-count fastball for a solo homer in the fourth. Rocker’s pitch count by the end of that frame reached 74, right around the threshold that the Rangers intended.

The two-time Top 10 pick in the MLB Draft was as advertised, generating 17 whiffs en route to seven strikeouts among the 17 batters he faced, with just three hits allowed. The Mariners had a chance to jump on him in the first, when Victor Robles and Julio Rodríguez reached scoring position. But they were stranded by three straight outs.

“Add-ons are important,” Mariners manager Dan Wilson said. “Again, I think our at-bats were good. We just weren't able to get anything else across.”

Even with the production in the fifth and 10 total baserunners, the Mariners struck out 16 times, their third-most in a game this season, and went 1-for-11 with runners in scoring position. Rodríguez was the last, fanning on three pitches vs. All-Star closer Kirby Yates in the ninth, with Robles -- who reached base four times and had a pair of steals -- on as the tying run.

“I was just trying to make really good contact over there,” Rodríguez told ROOT Sports. “And yeah, we do have opportunities, but that's kind of baseball. Sometimes, we're going to create traffic … and we're going to knock them in. Sometimes, we just won't.”

Seattle’s lack of insurance runs proved costly, but so were hiccups from Snider, Saucedo and Troy Taylor, who gave up a solo homer to Nathaniel Lowe in the seventh that sparked the Rangers’ rally. The rookie Taylor has earned trust in leverage, but each of his three runs since debuting on Aug. 11 have been via solo homers. Snider carried a 0.88 ERA since returning from Triple-A Tacoma on June 28. Andrés Muñoz was lined up for the ninth.

Rocker is the first of Texas’ three straight high-octane starters this weekend that will be on an abbreviated pitch count, along with Jacob deGrom and Max Scherzer, each returning from the injured list and a tandem that has a combined five Cy Young Awards. They’ll pose a big challenge, but their limitations should also give the Mariners an opportunity.

They also have to seize it, which continues to be a struggle.