Red Sox starter Drew Pomeranz made strides forward in 2017. However, a deeper look into the lefty’s season hints that this progress may have been a mirage.
On July 14, 2016, the Boston Red Sox dealt top prospect Anderson Espinoza to San Diego in exchange for a 27-year-old southpaw named Drew Pomeranz.
Many of the Boston faithful were furious that Dave Dombrowski moved a prospect that was drawing comparisons to Pedro Martinez for a pitcher who had yet to top 100 innings in his five seasons in the big leagues. A strong stretch run for Pomeranz may have squelched this anger, but his performance in the second half of 2016 only fanned the flames.
In 13 starts, Pomeranz managed to complete seven innings only once. According to Baseball Reference, the same man who posted an incredible 161 ERA+ with the Padres in the first half of 2016 pitched to the tune of a 4.59 ERA and 98 ERA+ in Boston. Between the perceived overpay Dombrowski gave to San Diego for his services and his own poor performance, Pomeranz became a common punching bag on Yawkey Way.
However, when 2017 rolled around, Pomeranz appeared to turn the corner. The lefty went 17-6 with a 3.32 ERA in 173.2 innings. One division title later, it seems that Red Sox nation has warmed up to Pomeranz.
As we turn the calendar to 2018, Pomeranz will be tasked with repeating this performance. Unfortunately, a deeper look into the Pomeranz of 2017 reveals that much of his success may not stick. While on a surface level Pomeranz was successful at keeping runs off the board, some of his peripherals raise red flags.
The first sign of regression that jumps out at me when looking at Pomeranz’s 2017 numbers is the difference between his ERA and his skill based indicators. Pomeranz’s FIP, xFIP, and SIERA were 3.84, 4.14, and 4.31 respectively per Fangraphs. These numbers suggest Pomeranz may have been lucky; a gap this large is often a sign that regression is on the horizon. It is known, however, that some pitchers routinely outperform their peripherals. Does Pomeranz fit into this category?
At first glance, Pomeranz’s numbers pass the smell test. He owned a .310 BABIP and 11.2% HR/FB in 2017. Neither of these paint him as particularly lucky, which is a good sign. He also struck out hitters at a strong clip of 9.02 per nine innings. But Pomeranz allowed a lot of baserunners this past season. In fact, his 1.35 WHIP placed him in the lower half of the league.
So with all these men reaching base, how was Pomeranz so effective at limiting runs? A Left On Base percentage of 80.0 could go a long way in explaining this phenomenon. 80 percent is annually near the high water mark for qualifying big league starters. The pitchers who consistently post marks in this vicinity share a similar profile to each other; notably, they strike out a lot of batters and allow very few to reach base.
Now looking back to that 1.35 WHIP, we may have serious cause for concern. Take a look at every qualifying pitcher since 1901 who has posted a LOB% of 80% or above with a WHIP of 1.30 or above.
| Name | Season | Team | IP | K/9 | BB/9 | LOB% | ERA | FIP | WHIP |
| Bob Buhl | 1957 | Braves | 216.2 | 4.86 | 5.03 | 80.8 % | 2.74 | 3.95 | 1.44 |
| Ruben Gomez | 1954 | Giants | 221.2 | 4.30 | 4.43 | 80.3 % | 2.88 | 4.18 | 1.40 |
| Roger Pavlik | 1993 | Rangers | 166.1 | 7.09 | 4.33 | 80.2 % | 3.41 | 4.35 | 1.39 |
| Al Leiter | 2004 | Mets | 173.2 | 6.06 | 5.03 | 81.0 % | 3.21 | 4.76 | 1.35 |
| Drew Pomeranz | 2017 | Red Sox | 173.2 | 9.02 | 3.58 | 80.0 % | 3.32 | 3.84 | 1.35 |
| Jarrod Washburn | 2005 | Angels | 177.1 | 4.77 | 2.59 | 81.8 % | 3.20 | 4.35 | 1.33 |
| Daisuke Matsuzaka | 2008 | Red Sox | 167.2 | 8.27 | 5.05 | 80.6 % | 2.90 | 4.03 | 1.32 |
| Casey Cox | 1969 | Senators | 171.2 | 3.83 | 3.36 | 80.0 % | 2.78 | 3.93 | 1.31 |
| Doyle Alexander | 1981 | Giants | 152.1 | 4.55 | 2.60 | 80.9 % | 2.89 | 3.43 | 1.31 |
| Sammy Stewart | 1981 | Orioles | 112.1 | 4.57 | 4.57 | 84.2 % | 2.32 | 4.11 | 1.30 |
The first thing you might note is that this is a very short list. Only 10 pitchers have achieved this feat since LOB% has been recorded and none prior to Pomeranz since 2008. Were these pitchers able to sustain this success? Let’s look at their performances in each of their follow-up seasons and find out.
| Name | Season | Team | IP | K/9 | BB/9 | LOB% | ERA | FIP | WHIP |
| Bob Buhl | 1958 | Braves | 73 | 3.33 | 3.70 | 73.5 % | 3.45 | 3.90 | 1.42 |
| Ruben Gomez | 1955 | Giants | 185.1 | 3.84 | 3.06 | 69.9 % | 4.56 | 4.05 | 1.46 |
| Roger Pavlik | 1994 | Rangers | 50.1 | 5.54 | 5.36 | 59.7 % | 7.69 | 5.99 | 1.81 |
| Al Leiter | 2005 | 2 Teams | 142.1 | 6.13 | 6.20 | 65.5 % | 6.13 | 5.16 | 1.77 |
| Jarrod Washburn | 2006 | Mariners | 187 | 4.96 | 2.65 | 69.8 % | 4.67 | 4.78 | 1.35 |
| Daisuke Matsuzaka | 2009 | Red Sox | 59.1 | 8.19 | 4.55 | 75.8 % | 5.76 | 5.09 | 1.87 |
| Casey Cox | 1970 | Senators | 192.1 | 3.18 | 2.06 | 68.3 % | 4.45 | 4.51 | 1.33 |
| Doyle Alexander | 1982 | Yankees | 66.2 | 3.51 | 1.89 | 57.0 % | 6.08 | 5.30 | 1.43 |
| Sammy Stewart | 1982 | Orioles | 139 | 4.47 | 4.01 | 71.1 % | 4.14 | 3.95 | 1.45 |
Well, that’s a concerning trend. Of the nine pitchers above, only three managed Left on Base percentages above 70%. For context, 72% is about average.
The takeaway from this is that Pomeranz probably won’t strand 80% of baserunners next year. There are positives here; Pomeranz had the second best FIP and far and away the best K/BB of this group supporting his 80% LOB percentage. But players who allow as many baserunners as Pomeranz aren’t usually as successful as he was in 2017.
Next: Free agency mistakes should make Dombrowski cautious
In 2018, something will have to give. Either Pomeranz will have to allow fewer baserunners or, more likely than not, he’ll give up quite a few more runs. With a slew of question marks facing their lineup, the Red Sox need their rotation to pick up the slack. It would be a great start if Pomeranz pitches like it’s 2017, but history shows that that level of success may not be what is in store for the southpaw.