Has new hitting coach Jeff Pentland made a difference on previous teams?

On Sunday night, news broke that the New York Yankees have hired a hitting coach and for the first time in franchise history an assistant hitting coach. What is also interesting here is that neither Jeff Pentland and Alan Cockrell have coached at the major league level in the last three seasons; Pentland having last coached in July 2011 and Cockrell, who will be his assistant, was last a hitting coach in mid-2010. This might be seen as concerning, but countering this with a clear positive; the Yankees took their time with this search, ultimately settling on two candidates who, by all accounts, had impressive interviews.

Assessing the effect a hitting coach can have on a team isn't straightforward, especially from outside the organization. There is reason for optimism with at least one former Yankee in Gary Sheffield, who previously worked with Pentland when they were both with the Marlins, giving him a ringing endorsement. The Yankees probably had the benefit of speaking to current members of the coaching staff Joe Girardi and Tony Pena, as well as potentially Carlos Beltran as well, all of whom have worked with Pentland in the past. Without the benefit of all this inside information, I'm personally quite happy to trust the organizational decision makers on this one.

Still, it might be interesting to look at the teams that Jeff Pentland has coached in the past. As it's difficult to normalize for different talent levels, I'm mainly looking at changes in the year before and after teams hired Pentland.

I'm going to exclude the single half-season Pentland had with the Florida Marlins in 1996, and include only the positions where he spent at least one full season.

Note: Best Hitters measured by wRC+ with an arbitrarily selected  minimum of 200 PA

Note 2 (well, warning): Lots of numbers, spoiler alert is not much changed. Scroll past the numbers for the summary.

Chicago Cubs - 1997-2002 (6 seasons)

Easily Pentland's longest tenure with a single team. You can consider their full statistics over the six seasons here on Fangraphs, but for this I'm more interested in 'before' and 'after' single-season comparisons.

'Before' Season (1996) :- 6229 PA, 175 HR, 8.4 BB%, 17.5 K% .251/.320/.401, .316 wOBA, 88 wRC+

Best Hitters (1996):- Mark Grace (127 wRC+), Sammy Sosa ( 125 wRC+) Brian McRae (108 wRC+)

First Season (1997) :- 6098 PA, 127 HR, 7.4 BB%, 16.4 K% .263/.321/.396, .315 wOBA, 83 wRC+

Best Hitters (1997):- Mark Grace (130 wRC+), Kevin Orie (101 wRC+), Sammy Sosa ( 93 wRC+)

Slight drop-off here actually, from 88 wRC+ to 83 wRC+ with Sosa, McRae and Ryne Sandberg all having significantly weaker seasons in 1997. Sosa is the the biggest culprit, and really, considering the year he had in 1998 when still working with Pentland, it's hard to pin too much on Pentland here.

Last Season (2002) :- 6242 PA, 200 HR, 9.4 BB%, 20.3 K% .246/.321/.413, .320 wOBA, 93 wRC+

Best Hitters (2002):-  Sammy Sosa ( 157 wRC+), Mark Bellhorn ( 135 wRC+) Fred McGriff (125 wRC+)

'After' Season (2003) :- 6187 PA, 172 HR, 8.0 BB%, 18.7  K% .259/.323/.416, .321 wOBA, 91 wRC+

Best Hitters (2003):-  Sammy Sosa ( 131 wRC+), Kenny Lofton ( 121 wRC+) Corey Patterson (113 wRC+)

Very, very slight drop-off without Pentland, with some roster turnover involved. Among players who stuck around, Sosa is the biggest culprit in his 'corked bat' season. He remained an above average hitter but his reduction in both performance and plate appearences probably accounts for the marginal decline by himself.  Not much to note otherwise, the Cubs had a much better year in 2003, thanks to the pitching staff.

Kansas City Royals - 2003 to 2005 (2.5 seasons)

'Before' Season (2002) :- 6206 PA, 140 HR, 8.4 BB%, 14.8 K% .256/.323/.398, .316 wOBA, 85 wRC+

Best Hitters (2002):-  Mike Sweeney (151 wRC+), Raul Ibanez ( 123 wRC+) Carlos Beltran (117 wRC+)

First Season (2003) :- 6239 PA, 162 HR, 7.6 BB%, 14.8 K% .274/.336/.427, .332 wOBA, 95 wRC+

Best Hitters (2003):-  Carlos Beltran (134 wRC+), Mike Sweeney (122 wRC+), Aaron Guiel ( 114 wRC+)

Big jump here, by both wOBA and wRC+. Largely the same cast as well. Side note: what I wouldn't give for a 134 wRC+ and 602 plate appearances from Beltran this season....

Last Season (First Half 2005) :- 3258 PA, 66 HR, 6.9 BB%, 16.3 K% .262/.319/.395, .313 wOBA, 87 wRC+

'After' Half Season (Second Half 2005) :- 2828 PA, 60 HR, 7.0 BB%, 16.6 K% .263/.320/.396, .313 wOBA, 87 wRC+

Best Hitters (2005):-  Mike Sweeney (122 wRC+), Matt Stairs ( 116 wRC+) David DeJesus (112 wRC+)

'After' Season-Full (2006) :- 6229 PA, 124 HR, 7.6 BB%, 16.7 K% .271/.332/.411, .323 wOBA, 92 wRC+

Best Hitters (2006):-  Esteban German ( 136 wRC+), Mark Teahen ( 123 wRC+) David DeJesus (110 wRC+)

Pentland was fired midway through the 2005 season. He didn't quite make it to the All-Star break, and the Royals did show slight improvement in July over their midpoint numbers, so the midway split I've taken - for simplicity more than anything else - is kinder to Pentland than it could otherwise be. Not by too much though, the Royals were already turning around their sluggish April by the time he was let go.

Beyond that, the Royals saw a slight but significant improvement the full season after Pentland left in 2006, but a big part of this was Esteban German who came over from the Rangers in the 2005 offseason. 2006 was so far and away German's best season it's incredible. A utility guy, playing everywhere, hitting to a 136 wRC+? Woah. Otherwise 2006 saw Sweeney and Stairs drop off but a young Mark Teahen improve significantly. It would have been nice to see if Teahen would have developed as much if Pentland had stayed.

Seattle Mariners - 2006 to 2008 (3 seasons)

'Before' Season (2005) :- 6095 PA, 130 HR, 7.6 BB%, 16.2 K% .256/.317/.391, .309 wOBA, 90 wRC+

Best Hitters (2005):-  Richie Sexson (144 wRC+), Raul Ibanez ( 115 wRC+) Ichiro Suzuki (106 wRC+)

First Season (2006) :- 6213 PA, 172 HR, 6.5 BB%, 15.7 K% .272/.325/.424, .322 wOBA, 95 wRC+

Best Hitters (2006):-  Raul Ibanez ( 121 wRC+), Richie Sexson (117 wRC+), Ichiro Suzuki (106 wRC+)

Another improvement here in Pentland's first season, by both wOBA and wRC+. The same names at the top, but a few improvements throughout the Mariner hitting roster, with Adrian Beltre in particular improving significantly. Kenji Johjima coming over from Japan and turning in above-average offense from the catcher position didn't hurt either. Overall, this was probably a push.

Last Season (2008) :- 6176 PA, 124 HR, 6.8 BB%, 14.4 K% .265/.318/.389, .310 wOBA, 90 wRC+

Best Hitters (2008):-  Raul Ibanez ( 122 wRC+), Adrian Beltre (106 wRC+), Jose Lopez (102 wRC+)

'After' Season (2009) :- 6113 PA, 160 HR, 6.9 BB%, 17.9 K% .258/.314/.402, .313 wOBA, 89 wRC+

Best Hitters (2009):-  Russell Branyan ( 126 wRC+), Ichiro Suzuki (125 wRC+), Mike Sweeney (105 wRC+)

This is a bit of a tough one. Russell Branyan came over as a free agent and was instantly the team's best hitter. Franklin Gutierrez and Mike Sweeney were also above average hitters in 2009, in their first seasons with the Mariners. Meanwhile Beltre saw his performance slip, and Richie Sexton was essentially a non-factor before being released midway through the season. Overall, the roster turnover probably benefited the Mariners and yet their overall  offensive production only really matched 2008, despite all of Branyan's home runs. If I had to score this one, I'd probably mark one down for Pentland. If I was keeping score that is. The important thing is I'd certainly not say the Mariners significantly improved by letting Pentland go.

Los Angeles Dodgers - 2010 to 2011 (1.5 seasons)

Pentland was hired by the Dodgers as a secondary hitting instructor in 2008, but for this I'll consider only his time as a hitting coach from 2010-2011. I chose to leave Cockrell out of this as he is the assistant head coach, so I'll be consistent and include only Pentland's time as a head coach.

'Before' Season (2009) :- 6385 PA, 145 HR, 9.5 BB%, 16.7 K% .270/.346/.412, .332 wOBA, 102 wRC+

Best Hitters (2009):-  Manny Ramirez (147 wRC+), Andre Ethier ( 129 wRC+), Matt Kemp (123 wRC+)

First Season (2010) :- 6140 PA, 120 HR, 8.7 BB%, 19.3 K% .252/.322/.379, .309 wOBA, 92 wRC+

Best Hitters (2010):-  Manny Ramirez (150 wRC+), Andre Ethier ( 132 wRC+), Rafael Furcal (126 wRC+)

A significant drop here, but largely driven by two players. Ramirez spent the bulk of the season on the disabled list, and lost his starting job by September. Kemp saw a significant drop in performance. Furcal had a big jump, but saw significantly fewer plate appearences as well. Overall, it's hard to pin too much of this on Pentland.

Last Season (First Half 2011) :- 3468 PA, 63 HR, 8.0 BB%, 17.9 K% .254/.318/.367, .301 wOBA, 92 wRC+

'After' Half Season (Second Half 2011) :- 2626 PA, 54 HR, 8.4 BB%, 17.8 K% .260/.327/.386, .314 wOBA, 100 wRC+

Best Hitters (2011):-  Matt Kemp (168 wRC+), Andre Ethier ( 122 wRC+), James Loney (110 wRC+)

Pentland was, for the second time in his career, fired midway.  His Dodgers team we producing relatively well though, and Andre Ethier spoke out against the firing, saying Pentland had been made a scapegoat. Perhaps unsurprisingly, Ethier was one of the hottest hitters in the first half. As he cooled in the second half though, Loney, Rod Barajas and Dee Gordon had strong second halves. Overall, the Dodgers were slightly but significantly better offensively in the second half, without Pentland.

If you read the spoiler, and jumped here, the biggest reason to be optimistic might be the improvement of a similar cast of hitters from 2002 to 2003 on the Royals, particularly one Carlos Beltran, then in his prime. Otherwise, mostly not much jumps out as changing. There's enough to be positive about if you read the numbers with an optimistic eye, but there were certainly no wild improvements.

Of course for all we know the interview may have unveiled anything from a strong theory on helping Brian McCann beat the shift, to noting some suspicious hitch in Stephen Drew's mechanics - I'm less optimistic about this one. Anyway by the time the Yankee season ends in late September - hopefully late October - we'll have formed opinions based on what the Yankee offense actually delivered in 2015. Still, if you're hoping at this point that the new hitting coach provides a big bounce-back from any of the Yankee hitters, it might be best to temper expectations. Maybe Pentland does help out, but ultimately it's probably going to come down to the hitters themselves to step up. Plus, of course, stay healthy.

This was of course only one way of looking at Pentland's history as a hitting coach. I've chosen to look primarily at team hitting records, and compare subjectively roster changes and individual hitter performance across years towards an attempt to explain any differences. I felt this was the most interesting comparison with respect to the 2014 Yankees and what we might see in 2015. Plus, I must admit, as an observer I was biased toward the midpoint. I was not expecting to see anything jump out here. I think if Pentland - or indeed Cockrell - was a hitting coach savant the MLB analytical departments probably don't let them stay unemployed for several seasons. If either was severely detrimental I wouldn't have expected the Yankees to hire them. With this exercise, I was looking to rule out either outlier case.

What do you think? Are you optimistic about the two new hitting coaches the Yankees have just hired? Were you hoping for someone else? Or do you simply not care about the position of hitting coach and find yourself waiting for next month when spring training starts?