SEATTLE -- As if the night wasn’t already stressful enough for George Kirby -- plagued by three walks, his first homer allowed in 14 starts and diminished spin and velocity on all his pitches -- it was compounded by the bevy of stress pitches that the rookie threw over four traffic-filled innings.

As such, Kirby's outing was halted shorter than he, or the Mariners, would have liked in a 4-3 loss to the Tigers on Monday night at T-Mobile Park, which put his status for the upcoming American League Wild Card Series in a more precarious position.

The loss, coupled with Toronto’s win over Baltimore, secured the No. 4 seed for the Blue Jays, ensuring that they’ll host a best-of-three Wild Card Series that will begin Friday. The Rays also lost, which trimmed the Mariners’ magic number to two to lock up the No. 5 seed, and with it, a trip to face their Canadian rivals. Regardless, Seattle will be on the road for the entire Wild Card Series.

• Postseason ticket information

Standings update: 87-72 (second AL Wild Card spot)
Games remaining: 3

AL Wild Card: The Blue Jays secured the No. 4 seed; the Mariners lead the Rays by 1 1/2 games for the No. 5 seed.
Seeding battle: Tampa Bay owns the tiebreaker over Seattle (5-2).

Julio Rodríguez went 3-for-4 with a 110.1 mph single in the first inning and an RBI double in the seventh in his return from a lower back strain that shelved him on the 10-day injured list -- a hugely hopeful and timely sign with the postseason only days away.

However, the loss of Sam Haggerty to a groin injury with two outs in the ninth inning put an even more sour taste on an already tough night for Seattle. Haggerty, the club’s best baserunner and arguably its most valuable bench piece, was on crutches postgame and will undergo an MRI on Tuesday morning.

“Haggs has had such a great season,” manager Scott Servais said. “He’s kind of like that spark-plug guy -- you fire him in there, and he makes things happen.”

But back to Kirby. The Mariners have already adjusted their pitching plans for Tuesday’s doubleheader now that home-field advantage is no longer in play, shifting from Marco Gonzales in the matinee and Chris Flexen in the nightcap to Flexen in the early contest and a bullpen game after. That would position Gonzales to pitch the regular-season finale on Wednesday, or it could be a current Minor Leaguer.

All of it points to Logan Gilbert being skipped and saved for the AL Wild Card Series. And if he earns a starting nod -- along with Luis Castillo and Robbie Ray -- that would likely shift Kirby into a relief role for the series.

“I expect to throw against Toronto. ... I would love to help the team win,” Kirby said. “I’m ready to go.”

The rookie right-hander was behind from the start on Monday, walking Akil Baddoo to lead off the game and finishing with three free passes, tying a season high he set in a start against the A’s on Sept. 22. Two of those walked batters came around to score, accounting for half of his runs allowed, including one on a two-run homer to Javier Báez in the third that came on a slider way off the plate that was more an outlying example of the slugger’s free-swinging approach.

It was the first homer that Kirby had given up since he yielded four to Baltimore on June 27. Since then -- and before Báez went yard -- Kirby had gone 75 2/3 innings (MLB’s longest active streak), made 14 starts in between, faced 309 batters and threw 1,162 pitches without giving up a long ball.

The slider that Báez connected on was out of the zone, but it also had little movement, a trend for the outing. The spin on the pitch was down 183 rpm from Kirby’s season average to 2,024 rpm, and his curveball saw a 158-point dip to 2,023 rpm. With his four-seam fastball, Kirby experienced a 1.6 mph dip from his season average, down to 93.8. When he came in the zone with his heaters, he left four up that turned into hits.

“My velo has been down a little bit, but I still feel sharp and I've been making pitches,” Kirby said. “So I'm super excited for what's to come.”

Yet, beyond the command, there were moments where Kirby visibly looked different from his fast-paced self, laboring into three-ball counts four times, battling through 32 foul balls and allowing nine of his 20 batters faced to reach.

Kirby’s workload management has been well-chronicled for months. On Monday, he reached 156 2/3 innings for the season (including the Minors), more than double his 67 2/3 thrown last year. Now, on the heels of a shaky start to finish a standout rookie season, what to do with his next turn is of intrigue for the Mariners.

“He'll get some down days and get a chance to kind of recharge his batteries, and he'll be ready for us in whatever role,” Servais said.