The Seattle Mariners have been in the unique position this season of looking down at the perennial powerhouse Houston Astros in the AL West standings.

As Seattle spent the first two months jostling with the Texas Rangers for first place in the division, the Astros stumbled out of the gates to a stunning 12-24 start. At one point, the Mariners led Houston by 8.5 games.

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But all of a sudden, the Astros are right back in the mix. Houston has moved back into contention by winning 12 of its past 17 games, while Seattle is coming off a 4-6 East Coast road trip and Texas has stumbled to a 3-12 stretch. The first-place Mariners have widened their lead over the Rangers to three games, but their advantage over Houston has dwindled to just 3.5 games.

The Mariners and Astros open a four-game series in Seattle on Monday night, which marks the second of four series between the AL West rivals this season. Earlier this month, the M’s took two of three from Houston at Minute Maid Park. With the Astros coming to town, here are three things to know.

Starting rotation’s injury woes

At the center of Houston’s early-season struggles has been a starting rotation that’s been decimated by injury issues and problems on the back end. The Astros’ starters rank 27th in the majors in ERA (5.09), 30th in WHIP (1.48) and 25th in opponents’ batting average (.259).

Three-time Cy Young Award winner Justin Verlander missed the first three weeks of the season with shoulder inflammation. Two-time All-Star Framber Valdez was sidelined for three weeks in April with elbow inflammation. Cristian Javier missed nearly a month with neck discomfort and is now dealing with forearm discomfort, which kept him from throwing his scheduled bullpen session Sunday, according to Matt Kawahara of The Houston Chronicle. That could put Javier’s scheduled start Tuesday night in doubt.

In addition, the last spot or two in Houston’s rotation has been a mess. Hunter Brown has a 7.06 ERA, rookie Spencer Arrighetti has a 6.93 ERA and J.P. France had a 7.46 ERA before being sent down to Triple-A.

Valdez is scheduled to start Monday’s series opener and Verlander is slated to start Thursday’s series finale, but the Mariners should have favorable matchups in the other two games, with Javier’s start in question on Tuesday and Brown slotted for Wednesday. Seattle also gets a break in dodging 30-year-old Ronel Blanco, who has a 1.99 ERA through nine starts in a breakout third season. Blanco started on Sunday in his return from a 10-game suspension for having a foreign substance in his glove, and thus won’t be available to pitch in Seattle.

Tucker leading the way offensively

The Astros rank 10th in the majors with 4.6 runs per game, but they sit in the top five in most other major offensive categories. They rank first in batting average (.264), fifth in on-base percentage (.330), fourth in slugging percentage (.421), fourth in OPS (.751) and tied for fifth in home runs (64).

Two-time All-Star outfielder Kyle Tucker has led the way, erupting for a torrid start that’s put him alongside New York Yankees superstar Aaron Judge as an early AL MVP favorite. The 27-year-old Tucker has an MLB-leading 18 home runs, including 11 homers in his past 23 games. He also ranks second in slugging percentage (.624), second in OPS (1.033) and fourth in on-base percentage, trailing Judge by slim margins in all three categories. Tucker went just 1-for-10 with one homer in the three-game series against Seattle earlier this month, but don’t expect those types of numbers again this week.

Tucker is one of four Astros in the top 25 of the AL in OPS, along with second baseman Jose Altuve (.821), shortstop Jeremy Peña (.803) and outfielder/designated hitter Yordan Alvarez (.799). Alvarez’s numbers are a bit down from his otherworldly stats the past two seasons, but he’s still a massive threat in the heart of Houston’s order — as the Mariners know all too well. Third baseman Alex Bregman, however, is off to the worst start of his career. The two-time All-Star is batting just .210 with a .601 OPS, which is nearly 250 points below his career average.

Hot-and-cold bullpen

The Astros’ bullpen was a major issue early in the season. Through May 8, Houston relievers ranked 24th in ERA (4.71) and 27th in WHIP (1.42). Since then, however, the unit has been among the best in the majors. The Astros have an MLB-best 1.60 bullpen ERA since May 9, which is 0.73 better than the next-closest team. They also have a 0.95 WHIP over that span, which ranks second in the majors.

The most dramatic turnaround in Houston’s bullpen belongs to five-time All-Star closer Josh Hader, who signed a five-year, $95 million contract with the Astros in free agency this past offseason. Hader struggled to a 6.14 ERA and 1.43 WHIP in his first 15 relief appearances this season, which included giving up a tiebreaking homer to Cal Raleigh in the ninth inning of Seattle’s 5-4 comeback win in the May 5 series finale in Houston. But after that outing, Hader regained his usual dominance. The hard-throwing left-hander has allowed just one run, two hits and two walks in 9 1/3 innings since May 9, while striking out 14 of the 32 batters he’s faced over that stretch.

First pitch Monday night is at 6:40 p.m. You can listen to all the action on Seattle Sports 710 AM or on the Seattle Sports app.

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