Stats help explain Cubs' second-half slump

MLB-worst grounder rate over final 2 months slowed offense

January 9th, 2019

Much has been made of the way the Cubs' offense sputtered over the final two months of last season. It is one of the primary reasons fans have been repeatedly clicking refresh on rumor roundups all offseason, hoping to see the North Siders linked even remotely to a certain blockbuster free agent of Nationals fame.
Since the Cubs' one-and-done appearance on the October stage, the leaders within Chicago's front office have also focused on the offense's collapse. Combined with an incredible late-season surge by the Brewers, the sharp decline in production played a large role in the 95-win Cubs settling for the top National League Wild Card spot as opposed to another division crown. The task at hand is identifying what went wrong and working on a solution.
"Part of getting better," president of baseball operations Theo Epstein said to reporters at a season-end sit-down, "is facing the problem, and our offense broke somewhere along the lines."
There was the impressive .265/.345/.426 slash line in the first half, followed by a concerning .249/.316/.389 slash after the All-Star break. It would not be fair to put the onus on and the left shoulder issues that sapped his slugging percentage and cost him multiple stints on the disabled list. This was a team-wide issue.
So, what happened? And what is being done about it?
Behind the numbers
Although one statistic alone can never tell the entire story, looking at the Cubs' ground-ball rate down the stretch cracks open the window of explanation.
Over the final two months of the season, Chicago's lineup posted a 47.8 percent ground-ball rate, which ranked last in the Majors. Looking through the Statcast™ lens, the Cubs' collective launch angle dropped to 8.8 degrees over the last two months -- down from 10.4 degrees in the first four months. So, while the team's average exit velocity was virtually identical in those two samples (87.8 mph over the first four months, then 87.7 mph the rest of the way), the Cubs' power production plummeted.
The biggest drop in slugging percentage came against fastballs. Over the last two months, the Cubs posted a .389 slugging against all variations of heaters (.445 was the MLB average for '18) and had a 9.2 degree launch angle. Those marks were down from .470 and 10.3, respectively, over the first four months. There were a few culprits driving this specific area of decline.
SLG vs. FB, last two months
: .164
: .250
: .297
Albert Almora Jr.: .303
Along the same lines, the Cubs' launch angle dropped in the final two months against breaking balls (9.4 degrees vs. 11.4 in first four months) and offspeed pitches (5.2 degrees vs. 8.9). In those two months, (.108 SLG vs. breaking balls and offspeed pitches combined), Russell (.158), Almora (.255) and Bryant (.258) had a notable decline in production. For reference, MLB hitters slugged .360 against breaking balls and offspeed pitches combined last season.
At the same time, Chicago's walk rate dropped to 7.7 percent in the last two months, compared to 9.7 in the first four. Overall, the Cubs posted an 86 wRC+ in that two-month sample, indicating that the offense was 14 percent below league average. That mark had been 106 from Opening Day through July.
"We hit more ground balls in the second half than any other team by a huge margin," Epstein said at the end of the season. "Our goal is to hit line drives and fly balls out of the ballpark. ... We stopped walking, we stopped hitting home runs, we stopped hitting the ball in the air, and we stopped being productive."
Addressing the problem
In many cases, hitters are who they are by the time they reach the Major Leagues. A team's job is to find a productive blend of offensive skill sets to create a well-rounded lineup. That does not mean that a team's philosophy can't be tweaked or an individual batter can't alter his approach or swing mechanics for the better.
Faced with budget limitations this offseason -- is not expected to walk through Wrigley Field's door unless some trades are made to free up payroll -- the Cubs have focused their attention on behind-the-scenes alterations. Veteran hitting coach Chili Davis was dismissed at the end of last season and Chicago quickly brought Anthony Iapoce (formerly a Minor League hitting coordinator for the franchise) back to the organization.
After assistant hitting coach Andy Haines left for the main hitting coach gig with the rival Brewers, the Cubs hired former big leaguer Terrmel Sledge to be Iapoce's second set of eyes. With the new coaching leadership in place, expect the Cubs to focus on the aforementioned areas in need of addressing.
It could help that Iapoce saw many of the current hitters' swings when they were developing in the Minors.
"You're always trying to lay down the groundwork and the foundation of what you're trying to accomplish as a team," Iapoce told after being hired in October. "Now, going back to somewhere that you're familiar with as far as players, coaches, front office, yourself, you can go in right away and be yourself and not be too concerned about looking over your shoulder coaching. You can coach right away."
Shortly before the Winter Meetings, Epstein was asked if the Cubs planned on targeting specific attributes while exploring potential additions to the lineup this offseason. While he said "good bat-to-ball skills and adjustability" were important, Epstein emphasized that the bulk of the improvement will need to come from within.
"No one hitter, especially in the seas where we're fishing, is going to transform the offense," Epstein said. "It's going to be a continued evolution of what I think is a group of really, really talented position players that stumbled badly in the second half of last year. And I don't think that's who we are. I think we're better than that."
To date, the only offensive addition to the MLB roster has been veteran utility man , but his hitting profile could incrementally correct some of the problems in the second half.

Descalso's .238 average in 2018 would be a deceiving way to describe his offensive ability. Over the past few years, the 32-year-old infielder has adjusted his swing to generate more fly balls, and the result has been improved power. Descalso had a 46.3 percent fly-ball rate, which was up from 36.9 percent over his career. Per Statcast™, Descalso also posted a 19.1 degree launch angle, following a 12.8 showing in '17.
Adding Descalso will not fix the offense, but it could be part of the solution. Chicago will also need Bryant back to his usual slugging ways, and every report on his progress this offseason has been positive. The Cubs will also be hoping for bounce-back showings from Contreras and Happ, plus more positive development from and Almora.
"There is some technique that I think is applicable to make these guys better," Cubs manager Joe Maddon said at the Winter Meetings. "But, I also think patience is required to permit these guys to get to the level of their competency. This is where I'm at with all this. So, conversationally, I've already talked to [Iapoce and Sledge] and I talked about specifics about what I think, and we're definitely, absolutely, on the same page."