By Cliff Corcoran

The most significant head-to-head matchup in Major League Baseball this week, and quite possibly for the remainder of the regular season, is taking place not in Los Angeles or Baltimore. It's in Seattle, where the slumping Blue Jays are attempting to hold off a Mariners team that thrust itself back into the American League Wild Card picture last week.

Monday's game, a 3-2 Jays win, put a significant dent in Seattle's chances of catching up, but it was thrilling, playoff-quality baseball, nonetheless. With Safeco Field packed with Blue Jays fans who had flooded across the border, Toronto got out to an early 3-0 lead on Taijuan Walker thanks to a two-out, two-run home run by Edwin Encarnacion in the top of the third and a leadoff double by Troy Tulowitzki that came around to score in the fourth. Jays starter Marco Estrada, who had struggled in his previous three starts, held Seattle hitless through six innings, thanks in large part to the spectacular play of Kevin Pillar in center field, before Robinson Cano broke a personal 0-for-13 slump with a leadoff single in the seventh. Seattle bounced Estrada and loaded the bases with two outs in the eighth, but Cano lined out against Blue Jays closer Roberto Osuna to end the threat. Then, in the bottom of the ninth, with Seattle down to its last strike, Leonys Martin hit a two-run home run to bring the Mariners within one only for Osuna to strike out rookie Ben Gamel to end the game.

That outcome pulled the Jays even with the Orioles and dropped Seattle three games behind that duo and into a tie with the Astros, who beat the A's 4-2. Entering Tuesday's action, both the Tigers, who have one fewer loss than Houston and Seattle, and the Astros have a better chance of stealing a Wild Card berth, per Baseball Prospectus's odds. But neither of those teams have any games remaining against either of the teams they are chasing. The Mariners, however, will host Toronto two more times this week, with Hisashi Iwakuma taking on J.A. Happ Tuesday night and Felix Hernandez facing Aaron Sanchez -- both pitchers coming off poor outings and Sanchez pitching on nine day's rest -- in the series finale Wednesday afternoon.

Pitching is what has thrust the Mariners back into this race. After a 10-7 loss to Texas on Sept. 6, Seattle was six games out of the second Wild Card spot. However, they won their next eight games, averaging just 2.4 runs allowed per game over that span. Their bullpen, which contributed 3 2/3 scoreless innings Monday night, has posted a 1.35 ERA over that span, second only to the Red Sox relief corps over the past 13 days.

The onus is now on Seattle's offense, which has scored more than two runs just once in their last five contests. Cano is a key figure there, as his slump extends beyond that 0-for-13 he snapped Monday night. Over his past 11 games, Cano has gone 6-for-43 (.140) with just one extra-base hit. Nori Aoki (14-for-38, .368, since reclaiming his starting job in left field) and Seth Smith (11-for-35, .314, with four home runs over the Mariners' last dozen games) have been getting the job done in the top two spots in the lineup, but Cano, who hits third, has not been following up. 

Unfortunately for the left-handed Cano and the lefty-heavy Mariners lineup, Toronto is rolling out a very effective left-handed starter Tuesday night. Happ is the first lefty starter the M's will have faced in nearly two weeks and will force Seattle to scrape the rust off of short-side platoon players Franklin Gutierrez (for Smith), Guillermo Heredia (for Aoki), and Dae-ho Lee (for first baseman Adam Lind). Gutierrez has made just one plate appearance since September 8 (he struck out). Heredia has been used primarily as a defensive replacement over that span, going 1-for-7 while not appearing before the sixth inning in any of the Mariners' last 10 games. Lee has drawn a couple of starts over that span, but with little more to show for it, going 2-for-13 without a walk. With middle-of-the order lefties Cano and Kyle Seager diminished against southpaws, that's not exactly the recipe for a breakout performance by the Mariners lineup.

Offense has been an uncharacteristic strength of this Mariners team all season. The one-run difference in Monday night's game is also the difference in runs scored between the Mariners and Blue Jays on the season. Seattle's 710 runs scored thus far this season are already the most scored by any Mariners team since 2007. That's ironic given the emphasis former general manager Jack Zduriencik placed on offense during his time running the team from late 2008 to late last year. Then again, the powerful core of the 2016 Mariners' lineup is one new GM Jerry Dipoto inherited from Zduriencik, with Cano, Nelson Cruz and Seager all enjoying exceptional seasons. As Monday night's game illustrated, however, the Mariners need contributions from the bottom half of the order, as well. 

One of the big successes of the new administration has been the rebooting of catcher and former first-round draft pick Mike Zunino's career. However, Zunino is just 1-for-15 over his last five games and has struck out in seven of his last nine plate appearances. Shortstop Ketel Marte has been a tremendous disappointment in his sophomore season, has now failed to reach base in his last 10 plate appearances and may yield to fellow switch-hitter Shawn O'Malley (.516 OPS in September) against the lefty Happ Tuesday night. The only Mariners regular with a lower on-base percentage than Marte's .291 has been Lind, who has reached base at a brutal .279 clip.

As disadvantaged as they may be against the lefty Happ, the next two nights are now must-wins for the Mariners. If they lose both, they'll be five games out with 10 to play. Even a split would put them in the unenviable position of being three out with 10 left (though two more Red Sox victories in Baltimore could put them two behind the Orioles in that scenario).

If they can win both, however, they'll pull within a single game of Toronto heading into a more favorable schedule than the Jays' over those final 10 games. After this series, Toronto has to run the gauntlet of the best teams in the AL East with four against the Yankees, three against the Orioles and the final three games of the season in Boston against the first-place Red Sox. The M's, by comparison, follow this series with three games in Minnesota against the Twins and finish the season with four at home against the A's. Seattle's only remaining challenge after this series is a three-game set in Houston against an Astros team that is not only currently tied with the Mariners in the Wild Card chase, but is 10-6 against them on the season.

For the franchise with the longest active playoff drought in the major leagues, this is an opportunity worth savoring. For the rest of us, it just might make the next two nights in Seattle the most compelling baseball we'll see until October.

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Cliff Corcoran is a Sports on Earth contributor and a regular guest analyst on the MLB Network. An editor or contributor to 13 books about baseball, including seven Baseball Prospectus annuals, he spent the last 10 seasons covering baseball for SI.com and has also written for USA Today and SB Nation, among others.