After taking two of three games from the Kansas City Royals, the Seattle Mariners find themselves with a 6-4 record and off to their best start through the first 10 games of a season since 2014 where they also began the year 6-4. 

The Mariners’ solid start to the 2018 season has them already four games better than this point last year, which saw the team struggle out of the gate with a 2-8 record.

So, what has been the difference between this year and last?

One could point to the offense, where the Mariners are averaging 4.4 runs scored per game, an increase from the 3.8 runs the team averaged last year over their first 10 contests.

The Mariners have also shown to be one of the better defensive units in the league, where their team UZR of 0.3 ranks 5th best in the American League, and their +6 DRS ranks 3rd best.  

There is also the fact that, unlike last season, the Mariners did not have the daunting challenge of facing the eventual World Series champion Houston Astros in seven of their first ten games.

While all of the above are factors, the biggest reason for the Mariners early season success has been their pitching.

Specifically, the ability of the rotation to hand the ball off to the bullpen with a lead, and the bullpen’s ability to, in turn, protect the lead and preserve the win.

Such an ability has been the plan GM Jerry Dipoto repeatedly talked about since the beginning of the offseason: to have a rotation good enough to get through a lineup two or three times, and then let the Mariners’ power bullpen take things from there.

And in the early going, the plan is working.

Mariners starters have pitched five or more innings seven times this season. In all seven games, the starter has been pulled with the game tied or with the Mariners in the lead. Only once has the bullpen given up the lead.

In other words, the Mariners are 6-1 when their starting pitcher goes at least five innings and leaves with the game tied or with the Mariners leading.

Compare that to the start of last season where the starting rotation was able to pitch five or more innings in all 10 games to start the year. In seven of those games, the bullpen was called upon either with the game tied or with the Mariners ahead. However, unlike what has occurred this season, the bullpen coughed up the lead in five of those seven games.

In other words, last season the Mariners went 2-5 when their starting pitcher went at least five innings and left the game tied or with the Mariners leading.

Of course, that is not to say the Mariners bullpen has been lights out this year. Their ERA (4.04) ranks eighth in the league, while their FIP (3.87) and WAR (0.3) both place 10^th in the league.

Clearly, the bullpen is giving up runs here and there. The difference is that while they do give up a few runs, the Mariners bullpen has shown the resiliency to not give up the go ahead run(s) when the game is late and close.

The Mariners bullpen has been the beneficiary of a “bend but don’t break” strategy that has seen their relievers progressively diminish hitters in the 7-9 innings.

To illustrate, the Mariners are allowing a .317 batting average in the 6^th inning. That average falls to .279 in the 7^th inning, and to .237 in the 8^th inning.  

In the 9^th inning, with the electric Edwin Diaz closing things out, opponents are hitting just a miniscule 0.83.

Overall, in innings 7-9, Mariners pitchers have tossed 27 innings, are allowing just a .219 batting average against, have issued just 5 walks, and are producing a 6.40 SO/W ratio.

In high leverage situations, the Mariners are holding opposing batters to a .203 batting average and putting up a 5.00 SO/W ratio.

In late and close situations? A .194 batting average against and a 6.33 SO/W ratio.

With those type of numbers, the Mariners have essentially shorted the game to just six innings in the early going.

Despite the cries and complaints by critics of not adding “impact” to the rotation, or being “cheapskates” by not spending to acquire another middle to back end starter, Dipoto stayed true to his vision of a healthy rotation being good enough, and a talented bullpen able to take the ball and close things out.

Whether or not this early season success is sustainable over the next 152 games is unknown. But so far, the plan is showing to be effective for the Mariners.