To begin with a gross oversimplification of a maddeningly complex sport, there are two ways to win a baseball game: score runs and prevent runs. Those two acts inform the predictive significance of run differentials and Pythagorean record and represent the reason I enjoy perusing leaderboards to see which teams are currently the best at run generation and prevention. We’re at the point in the season where the tops of the leaderboards aren’t terribly surprising – the Red Sox score frequently, the Mets don’t allow many runs, the Cubs are ridiculously great in both categories – but one team I’m still getting accustomed to finding near the top of the runs-scored leaderboard is the Mariners.

After years of battling mediocrity and a frustrating relegation to relative baseball obscurity, the Mariners have scored more runs than any American League team not named the Red Sox. With 315 runs scored through 63 games played, the Seattle is now averaging five runs scored per game — a rate they haven’t sustained over a full season since averaging 5.02 runs per game in 2002… you know, back when they had a designated hitter named Edgar Martinez, a second baseman named Bret Boone and a catcher named Dan Wilson. As offense has declined around the league during the last decade and a half, the Mariners’ offense has more than followed suit. In all but one season from 2004 to 2015, the Mariners finished anywhere from 11th to 14th in the AL in R/G. (Recall that, for a majority of that stretch, the American League consisted of only 14 teams.)

But now they’re scoring five runs a game – and are on a pace equivalent to 810 runs over a full 162-game schedule. Only five teams in the past five seasons have scored 810 runs and, of those five, all but the 2011 Red Sox made the postseason. And you might remember that the 2011 Red Sox team had to work darn hard to not make the playoffs. What the Mariners are doing right now is an undeniably good thing, and one that’s very much conducive to winning. And a little further digging reveals something endearingly quirky about the way the Mariners are scoring all of their runs.

As one might expect, the Mariners rank in the top five in the American League among key offensive categories, including batting average, on-base percentage, slugging percentage, and home runs. However, they also rank dead last in one surprising category: doubles. In fact, the Mariners have hit more home runs (94) than doubles (89). If you think that’s atypical, you’re correct.

Teams With More Home Runs Than Doubles Team Year G HR 2B Difference SEA 2016 63 94 89 +5 MIN 1963 161 225 223 +2 DET 1962 161 209 191 +18 NYY 1961 163 240 194 +46 LAD 1958 154 172 166 +6 CIN 1956 155 221 201 +20 NYG 1947 155 221 220 +1 SOURCE: Baseball-Reference (since 1913)

It’s been more than half a century since a team hit more home runs than doubles. It’s a feat so rare that it’s hard to believe the Mariners aren’t due for a bit of course correction along the way. Let’s take a look at how they’re doing what they’re doing and where we might expect changes going forward.

One of the first things to consider when discussing the Mariners’ power output is their ballpark. For the first decade of Safeco Field’s existence, it was considered an extraordinarily pitcher-friendly park. Since moving the fences in prior to the 2013 season, however, the park has played increasingly neutral. No offensive category in Safeco has seen a bigger jump by park factor than home runs, which has increased from 92 to 98 (100 represents league average). The Mariners wanted their home stadium to yield more home runs and they made it happen.

One interesting subset of park factors is the handedness factors. An obvious example of the potential extremes of handedness park factors is Fenway Park, where the Green Monster causes the park to play extraordinarily different for right-handed batters than left-handed batters. Throughout its existence, Safeco has been an easier park for left-handed hitters to hit a home run in than right-handed hitters, although that gap has begun to decrease since the fences were moved in.

Whether with that stadium tendency in mind or not, the Mariners have built a lineup which relies heavily on left-handed bats, beginning with the two bats they’ve locked up long-term: Robinson Cano and Kyle Seager. In fact, there are only currently two right-handed bats in the Mariners’ standard lineup: catcher Chris Iannetta and designated hitter Nelson Cruz. Although, their soon-to-be 34-year-old rookie Dae-Ho Lee is another righty and is currently making making a heckuva case to play everyday with his 147 wRC+ and neutral platoon splits. Regardless, it’s a lefty-heavy lineup in a park with a slight home-run advantage for left-handed hitters. Could this account for the outburst of home-run power?

It’s a decent theory, but the numbers don’t back it up. Mariners lefties have accounted only for 56 of the team’s 91 home runs, with 29 coming at home and 27 coming on the road.

So, what’s the source of the HR/2B disparity? The biggest factor is the aforementioned right-handed bat making a play for an everyday role: Dae-Ho Lee. Now a little more than two months into his major-league career, Lee has been winning over Seattle fans with a strong start including a walk-off home run back in April and a two-home-run game last Friday. His batting line, however, contains this oddity: 10 home runs… and zero doubles. According to Baseball Reference, no hitter has ever had a season with double-digit home runs without recording a double. It’s only a matter of time before Lee’s HR:2B ratio begins to normalize and the Mariners’ HR:2B will begin to normalize right along with it.

The Mariners are in the midst of an offensive surge we haven’t seen from them in a painfully long time and power has been a delightful part of it. While it’s reasonable to expect some regression in the career-best ISOs from Cano (.285) and Seager (.227) — in addition to Lee’s power returning to Earth — there’s simply no reason to expect the Mariners offense to fade away. Now two years into a career resurgence no one saw coming, Nelson Cruz continues to be a perennial 40-homer threat, and he partners with Cano and Seager to form a formidable middle-of-the-order along with impressive complementary players like Seth Smith, Adam Lind, and even Leonys Martin.

The big question for the Mariners is whether they will be able to pitch enough to remain competitive through the summer — and it’s a question with an answer that’s increasingly scary as Felix Hernandez’s health woes continue. Our projection system believes in what this team is showing and projects them to score 4.7 runs per game while conceding only 4.3 the rest of the way. The result? A 45.7% probability of making the playoffs. However, it’s worth noting that that figure includes significant production from King Felix. Quirks aside, this is very much a team worth monitoring right now, even as some of those home runs start turning into doubles.