HOUSTON -- The Mariners have shown themselves to be a playoff contender, but they continue to be shown who runs the American League West -- the Astros.

It was just before the All-Star break when Seattle was the hottest team in the Majors, as it was on a 14-game winning streak, the team’s longest in 21 years. The next challenger was Houston, which not only ended the Mariners’ winning streak but also swept them at T-Mobile Park and proved the division runs through the Astros.

Thursday marked the Mariners' first chance to correct what happened in Seattle, as they started their four-game series against the Astros at Minute Maid Park. Heading into the series, it had a lot of the same circumstances as last time: the Mariners having the better form (as they swept the Rangers, while the A’s swept the Astros) and a chance to lessen the gap in the AL West.

The stakes were set for the first game of the final regular-season series between the two, and the outcome was similar to what happened in Seattle, as the Mariners fell to the Astros in the series opener, 4-2.

“It’s just one of those games,” manager Scott Servais said. “It came right down to the end, and unfortunately, the last few against the Astros have not been in our favor.”

The one thing that did go Seattle’s way was its pitching. A big reason for the Mariners' recent success in their 17-4 stretch has been the club's work from the mound, especially from the bullpen, which leads the Major Leagues with a 2.01 ERA since June 21.

The bullpen’s success has paired well with what the starting staff has done, especially Logan Gilbert, Thursday's starter. Gilbert has proven himself as a quality starter in the rotation, and he joins Félix Hernández as the only pitcher at age 25 or younger to post 10+ wins, 100+ strikeouts and a sub-3.00 ERA in his first 20 starts to a season in team history.

It comes as no shock that the Mariners have had the success they had during the righty’s starts, as he has a 10-4 record, with a bit of that success coming in three previous games against Houston this season. It was the second time he faced the Astros in five days. On Saturday, he allowed two runs on five hits and one walk in six innings.

Gilbert had his struggles early in their matchup in Seattle and did again in Houston, as an 87.1 mph slider that did not hit the outer part of the plate as he was hoping for led to a Alex Bregman two-run homer in the first inning. He dominated the rest of the way, as he finished with six strikeouts while allowing two runs on five hits and two walks in six innings.

“Logan threw the ball extremely well,” Servais said. “Obviously, he made that mistake leaving that slider on the inside part of the plate, but after that, it was outstanding. I can’t say enough of what he continues to do for us.”

The job done by Gilbert was not matched by the Mariners’ offense, which has struggled against the Astros' pitching. That was magnified in Seattle when they scored eight runs in the three-game series.

The struggles continued Thursday, as after the two-run third inning -- with a sacrifice fly by Ty France and an RBI groundout by Carlos Santana -- they were unable to get much more done. Their five-hit night was best summed up by Servais after the game: They had their chances but not a ton of work offensively.

The shortcomings from the offense and the two runs Andrés Muñoz gave up in the eighth inning led to the Mariners losing the opener. The game showed two things about the club.

1. Their recipe of success of solid pitching and just enough runs works against most teams but may not work against the Astros, especially at Minute Maid Park.

2. The pitching is playoff caliber, but they need the offense to reach that caliber more consistently.

The offense has three more games in Houston to turn things around. The Mariners want to come out of this series knowing that they can face a team with playoff experience like the Astros and win, that they are a playoff-caliber team that is capable of snapping their 21-year playoff drought and with an idea of what holes they need to fill prior to Tuesday's 3 p.m. PT Trade Deadline to make their playoff dream a reality this season.