Just to be clear, this is the 2016-2017 offseason. I know you might be confused, considering you probably read three or four articles with similar titles before the 2016 season started. If you know anything about Jake Lamb, you already know how that ended up.
At the All Star Break in 2016, Jake Lamb was among the top ten players in the NL. Looking at his first half numbers are almost surreal: 151 wRC+, .322 ISO, 20 HR, 61 RBI, and a gaudy .612 slugging %. He was on pace for an MVP-ish season and his exclusion from the NL All Star roster was seen as a massive injustice and one of the biggest snubs in years. I'm not able to see inside Lamb's mind to confirm, but I would guess he was feeling pretty good about the way his season was going...and then the second half happened.
After the break, Lamb dropped off a cliff. In the second half, his wRC+ dropped all the way down to 68, his power withered away resulting in a meager .184 ISO, and he managed to slug just .380 while putting up 9 HR and 30 RBI. He was literally half the player in the second half. This begs the question: What's wrong with Jake Lamb?
Pouring through the stats from Lamb's 2016 season, a few things immediately jump out as possible causes for the tremendous regression. The most notable is his pull rate. During his red-hot start, Lamb was pulling the ball 50.5% of the time he made contact. After the break, that rate plummeted to 35.1%. At the same time, his fly ball percentage jumped from 33.8% to 40.3%. Essentially, Jake Lamb went from crushing balls to right field more than half the time he was making contact, to making weaker contact on fly balls to center and left. This doesn't completely explain the regression though, because Lamb was still getting positive results on his contact to center and left more often than not. The important takeaway is that these regressions are symptoms of the larger problem, rather than being the problem themselves.
The real problem was more likely the left hand injury that Lamb suffered in early August that nagged him throughout the month and into September. For left handed batters, the action of the left hand is what allows them to control the bat and roll over a pitch to make solid contact. To clarify, this isn't a mechanic unique to lefties, as the right hand serves the same purpose for right handed batters. One of the inherent advantages of batting left handed, however, is the ability to pull the ball and have it find the gap between first and second, as compared to right handed batters who often find the shortstop instead when they do the same thing. Therefore, being able to pull the ball as a leftie is extremely valuable, and by taking a look at Lamb's heat charts between the first and second half we're able to see where this advantage fell apart for him.
On the left is Jake Lamb's first half heat map, and on the right is Jake Lamb's second half heat map. Immediately we're able to see a major difference. After the second half, Lamb struggled to make contact with pitches up in zone, and especially on pitches up and in on his hands. These are the kinds of pitches that are easiest to turn on and pull for a leftie, so it stands to follow that his overall performance suffered as a result of his inability to make his most advantageous kind of contact.
So at this point you're probably confused, because I've just finished saying a great many negative things about Jake Lamb, yet I started off by saying that the NL West should be afraid of Jake Lamb. So let me go ahead and apologize, because I haven't really told you the whole story. To get into the meat of the issue, let's start with an extremely simple graph.
Above is a graph of Jake Lamb's wRC+* by month as indicated by the blue line. On the same graph is the league average wRC+ (which is always 100 by virtue of the nature of the statistic) indicated by the orange line. Now the puzzle begins to come together because we can see just how much of an outlier the month of August was for Lamb. If you remove August from the equation altogether, Jake Lamb was well above average throughout the season. It's no coincidence that Lamb was struggling with that hand injury throughout August and it coincided with the worst single month of his young career.
There's another wrinkle to consider however. Throughout August and September, Lamb's pull rate didn't recover to what it was prior to the break. He posted a 32.6% pull rate in August and a 31.3% rate in September through the end of the season. Despite this, Lamb's BABIP* improved a whopping 40 points between August and September, suggesting that he was at least partially recovered from his injury and was starting to make adjustments to compensate for his still-reduced bat speed.
So Lamb rebounded at least a little bit in September, and now has the offseason to fully recover and adjust his swing as needed. Adjusting his swing is something that Lamb has shown himself to be extremely capable of already, as one of the biggest stories out of Arizona last offseason was about how the young 3B retooled his swing to be more similar to teammate A.J. Pollock. The improvement certainly showed as Lamb posted the best offensive numbers of his career in the first half of 2016. If he can make another adjustment half as good, or simply just recover to where his swing was in 2016 until August, we're going to see one of the most dangerous trends of Jake Lamb as a batter really come to the forefront in 2016.
That trend is the simple fact that Jake Lamb absolutely murders fastballs. In 2016, Lamb produced an average 1.27 runs per 100 2 and 4 seam fastballs seen (good for 13th in the NL) and a staggering 9.97 runs per 100 split-finger fastballs seen (9th in the NL). Now we've reached the point where the NL West should be afraid, because if you look at the pitch distribution of every pitcher in the NL West who doesn't wear an Arizona Diamondbacks uniform, they combined to throw a 2 seam, 4 seam, or split finger fastball more than 60% of the time. Considering how effective he was at the plate when healthy in 2016, and the fact that he has improved immensely as a hitter in each of his three seasons in the majors so far, it's safe to say that the Rockies, Padres, Giants, and Dodgers should be very, very afraid of the young man at third in the Arizona desert.
*wRC+ (weighted runs created plus) measures how a player's wRC compares with league average. League average is 100, and every point above (or below)100 is a percentage point above (or below) league average
*BABIP (Batting average on balls in play) measures how many of a batter's balls in play go for hits, or how many balls in play against a pitcher go for hits, excluding home runs