What has gotten into the Mariners?

Seattle won again Thursday afternoon, in dramatic fashion. Trailing the Royals by margins of 4-0 and 6-3 in Kansas City, the Mariners tied the game on Mitch Haniger’s two-run triple with two outs in the ninth, then scored the winning run on Daniel Vogelbach’s solo homer in the 10th. The 7-6 victory pushed the M’s to 13-2, giving them six straight wins to end their road trip.

This was a club few expected to challenge for an American League West title, on the heels of an offseason of restructuring that included the departures of several prominent players. And yet, Seattle holds a four-game division lead over Houston, heading into the teams’ three-game series that begins Friday night at T-Mobile Park.

At this early point in the season, the Mariners have produced MLB’s best record and largest run differential, homered in every game, and scored an average of nearly eight runs scored per contest.

Here is a look at where their success in those categories stands historically, and what it might mean for their outlook in the rest of 2019.

Record
A 13-2 start is a rare feat. The Mariners are only the 17th team since 1900 to win at least 13 of their first 15 games in a season -- or about one team every seven years.

This type of hot start tends to bode well. Of the 14 previous clubs to start at least 13-2 since the first World Series -- excluding the 1994 strike year -- eight won their division, and four brought home a championship.

Since the Wild Card was established in 1995, all three teams starting 13-2 have become division winners. The most recent example happened just last year, when the Red Sox rode the wave of their 13-2 start to 108 victories, then rolled through the postseason to capture a World Series title.

The only team in the divisional era to miss the playoffs after such a season-opening surge was the 1987 Brewers. But that Milwaukee club still won 91 games, third best in the AL, and likely would have reached October in today’s Wild Card format.

Best 15-game starts in divisional era
(Since 1969)
2018 Red Sox, 13-2: Finished 108-54 (won division, World Series)
2013 Braves, 13-2: Finished 96-66 (won division)
2003 Giants, 13-2: Finished 100-61 (won division)
1994 Braves, 13-2: Finished 68-46 (no postseason -- strike)
1987 Brewers, 14-1: Finished 91-71 (missed playoffs)
1984 Tigers, 14-1: Finished 104-58 (won division, World Series)
1982 Braves, 13-2: Finished 89-73 (won division)
1981 A’s, 14-1: Finished 64-45 (won division)

Home runs
The Mariners have been hitting the ball over the fence a lot. We already know that their 15-game home run streak is the longest in Major League history to start a season, and their total number of homers is notable, too. Seattle’s 36 big flies ties it with the 2000 Cardinals for the most by a team through its first 15 games of a season.

But early power prowess does not necessarily correlate to postseason success, or even a playoff berth. There have been six prior teams to hit 30 or more home runs in the first 15 games of a season in the divisional era. Of those, just two made the playoffs that year -- those 2000 Cardinals and the ‘04 Cardinals (34 homers). Neither of those St. Louis clubs wound up leading the NL in long balls, and neither won the World Series.

Runs scored
With all of their wins and home runs, it stands to reason that the Mariners have scored a lot this season -- and indeed, they have. They’ve plated at least six runs in all but two of their games. Seattle’s 117 runs through 15 games is the second-highest total for any team since the first World Series in 1903.

The only team to score more runs through 15 games in that span was the 1962 Cardinals, who scored 122. That team finished 84-78 and did not play in the postseason.

However, the three teams directly behind the Mariners on that list -- the 2000 Cardinals with 114 runs, the 1932 Yankees with 114 and the 1995 Rockies with 113 -- each made the playoffs, with the Yankees winning the World Series.

Run differential
Seattle’s pitching has not exactly been dominant, and its defense has not helped the cause. The club’s 3.98 ERA ranks eighth in the AL, its 21 errors are by far the most in the Majors, and it has allowed at least five total runs in nine of 15 games.

Yet, combined with the aforementioned offensive outburst, the Mariners still have posted an MLB-best plus-42 run differential. That’s an average margin of nearly plus-3 runs per game. Thursday’s win was their fifth one-run victory, but they also have four blowouts of at least five runs.

That run differential ties Seattle for 11th-best through a team’s first 15 games in the Wild Card era. Of the 13 previous clubs to be at plus-42 or higher in that span, nine made it to the postseason, including two of the past three World Series champions -- the 2018 Red Sox and ‘16 Cubs.

Yet Mariners fans only have to look back to last year, within their own division, for a cautionary tale. The 2018 Angels were 12-3 with a plus-46 run differential, but ultimately finished 80-82 while allowing one run more than they scored.