Determining who and what to trust in the Mariners bullpen

Since the All-Star break the novas shining brightest have been the Mariners bullpen. Their results were sterling in Chicago, and as anyone who has seen a remastered ROOT Sports knows, the bullpen as a whole has been an asset over the last couple months.

As Kate touched on yesterday, the bullpen has made a significant turnaround, but for a unit that has used 24 pitchers as relievers, plus Mike Freeman and Carlos Ruiz, the growth has not come from new blood delivering upgrades, it has been the expected studs finally performing and getting results. Strikeouts are up, balls in play are down, but most importantly dingers allowed have dissipated. While it is a somewhat arbitrary date to select, the date Edwin Diaz returned to the closer role is as reasonable a point of delineation as any for the two seasons the M's bullpen has had so far.

The team's results have obviously been outstanding, as their ERA has been brilliant of late. Some of that improvement comes from replacing Casey Fien and Co. with Steve Cishek, Tony Zych, and, well, just a ton of poor Nick Vincent, who we'll talk a bit more about in a moment. The team has struck out opponents more often as well, while still running one of the lower BB-rates in the league. While Diaz has made mechanical adjustments, the biggest development for he and most of the staff has simply been that hard hit balls have been falling into gloves instead of the stands. In the midst of the fly ball revolution, Mariners relievers consistently felt their necks meet with a a guillotine blade over the first couple months as home run after home run altered the course of the season in the later innings. The team's hard hit rate allowed has actually increased (29.3% to 29.6%, 11th and 9th best respectively in their time frame), but by giving up fewer line drives, more pop ups, and more hard grounders, the M's have seen their results trend positively.

Bad pitches turn into home runs more frequently than good ones, but there is there is not as clean of a correlation between home runs and pitcher performance as we might think. As much as Edwin Diaz's high-profile struggles with dingers have been infuriating, their recent evaporation have not necessarily been the result of better process; simply better results from overpowering stuff. Nick Vincent represents the other end of the spectrum, where a man armed with nothing but a 90 mph fastball with an above-average spin rate has been one of the best relievers in baseball, and has somehow managed a 2% HR/FB rate despite giving up air outs 65.5% of the time.

The Mariners bullpen has gott-wait Nick Vincent has done what?

Fangraphs

Good grief. Since batted ball data has been tracked, Nick Vincent is among only eight pitchers to give up under 2% HR/FB despite giving up as many fly balls as he does. Vincent's success is likely to taper off somewhat, but the support of a healthy and locked in pen around him means the team is more likely to see decent stability in later innings going forward.

Tony Zych, James Pazos, Marc Rzepczynski, Steve Cishek, Nick Vincent, and Edwin Diaz all have the skills to be above-average relievers. The return of Shae Simmons, whose rehab saw him called up to Tacoma yesterday, should further bolster the unit. All of this could fall apart rapidly, as bullpens are wont to do, but the framework is there. For the Mariners to be a competitive team the rest of 2017 and in the next couple years, they need their bullpen to be a strength. For the first couple months we saw what happens when it's not. If they can continue to rise to the occasion and find better results as their talent level indicates they are capable of, we will see more series' like this weekend's. If the longballs return, however, the dog days will be bleak.