SEATTLE -- What already figured to be long-shot playoff hopes for the Mariners turned into a Herculean task on Tuesday when the Astros rolled to a 6-1 victory that has Seattle one loss from being eliminated from postseason contention.

The rebuilding Mariners only found themselves in this situation by going 16-11 since Aug. 21, while the Astros were losing 12 of their last 18 games to fall into tenuous territory even with MLB’s expanded 16-team playoff format.

• Box score

But the Mariners headed into their final week with a chance to make things interesting, if they could sweep a three-game series with the Astros. Step one fell in place with Monday’s 6-1 victory behind a dominant outing by Marco Gonzales, but Houston rebounded on Tuesday behind a five-run sixth against Seattle’s bullpen.

The Mariners close out the series with Houston on Wednesday at 3:40 p.m. PT before heading to Oakland for a four-game weekend set.

Seattle actually has a faint heartbeat in pursuit of Toronto for the AL’s final Wild Card berth as the Blue Jays lost to the Yankees, 12-1, and remain four games ahead of the Mariners for the No. 8 seed, but the math obviously is daunting in either case for a team with a 24-31 record.

The youthful Mariners have been realistic about their situation all along, but the expanded postseason format and their improved play after a 7-18 start to the season created some intrigue and added meaning for the September stretch.

“We’ve put some nice streaks together, and everybody got excited that we had a chance to make a run at the playoffs,” manager Scott Servais said. “Certainly we felt it. That’s a good thing for players to go through that and experience that.

“But understanding where we are as an organization, in our plan and our development, it’s really important these games are meaningful and players are getting better. That was the whole plan all year, to continue to get better, and I believe we have. There’s going to be nights like tonight -- you’re running a 23-year-old starter out there and trying to piece it together and it just doesn’t happen for you. But I’m very happy with the way we’ve been playing.”

Rookie right-hander Ljay Newsome held Houston to one run on four hits over 4 1/3 innings, but he’d totaled just 4 1/3 innings over the previous 25 days due to postponements and a line drive off his pitching hand. Servais went to his bullpen after Newsome reached a season-high 66 pitches, but Casey Sadler and Brandon Brennan both gave up home runs in a five-run sixth to seal the deal for Houston.

Newsome never pitched above Double-A prior to this season, and he is only in the rotation because of the midseason trade of Taijuan Walker to Toronto last month. But the young right-hander has learned a lot by being thrown into the mix.

“Just take as much in as I could and learn as I went, and it sets me up for next year, knowing what I need to do to keep improving myself,” he said. “I could see how my stuff plays to other big league teams.”

Newsome has been a strike-thrower at every level, but he knows he needs more than just his impeccable command. He didn’t walk a batter on Tuesday, but he struck out just one, the last batter he faced.

“I need an out pitch,” he said. “I need something that is sharp that shoots down. I went to Gas Camp and worked on my velo and got that up. Now I just need that one pitch to put guys away, because I’m always throwing strikes in good counts, so I just need that one pitch to put guys away.”