This time of year it’s always fun to start looking at some of the players who took big steps forward production-wise in the second half. It’s a valuable exercise for dynasty leagues, as it can be a big help in setting up early off-season target lists and getting a head start on thinking about keepers for next season. So today a simple exercise: I’ve sorted out the top 20 hitters in baseball for the second half by wOBA, and below are four who have performed most dramatically better than their first half efforts. Let’s take a look and see if we can identify anything helpful in the profiles of these guys.

Starling Marte, OF PIT (.324/.408/.562, .424 wOBA, 8.3 BB%, 16.7 K% in 120 PA’s)

Drafted as the 18^th outfielder and 55^th overall player off the board in NFBC drafts this spring, Marte entered the season with high expectations. Things didn’t go quite accordingly to plan, however, as he limped his way to real-life league-average production amid a strikeout rate increase of about 4% and despite an inflated BABIP in line with last season’s mark. Well, he’s since repaid the owners who stuck with him through the thin with a thick second-half in which he’s lopped a full 11% off his whiff rate   while crushing line drives on an impressive percentage of both fastballs and breaking balls. One area he’s remained highly vulnerable has been against good change-ups, as he’s shown an incredibly aggressive approach with precious little return. The league oddly hasn’t appeared to catch on to this vulnerability, as he hasn’t seen much at all in the way of a heavier dose of changes in response. The 28% line drive rate he’s mustered against the current pitch mix looks unsustainable in its own right, let alone once the league’s pitchers presumably make some adjustments this off-season. Marte’s improved contact and walk rates are both cause for celebration, and at 26 next year he’ll be right where you want him as a player squarely into his prime. The drop-off in speed production is troubling, though not uncommon over the second half of a season.

Verdict: His second half gains don’t appear entirely sustainable, though he’s made enough seemingly legitimate progress to where his pre-season valuation looks about right heading into next season if we assume he returns to a 30+ steal pace.

Nolan Arenado, 3B COL (.310/.371/.560, .404 wOBA, 7.5 BB%, 10.7 K% in 187 PA’s)

After missing a chunk of time in the first half of the season Arenado has really come into his own over the past couple months, checking in 11^th in the majors in wOBA over the second half. He’s exactly the type of player who benefits the most from Coors Field, as his power tool is solid-average in a vacuum. Sure enough, 14 of his 15 homers on the year have come at home and he’s posted a cumulative OPS for the season more than 200 points higher in the Rocky Mountains. Of note in his second half performance, he’s taken a significant step forward in laying off breaking balls out of the zone while becoming correspondingly more aggressive on fastballs. It’s resulted in a nice boost to his walk rate at the same time his already-stellar whiff rate has inched down a further tick. Small sample noise notwithstanding, strikeout and walk ratios stabilize between 150 and 200 plate appearances, meaning it’s entirely possible at this point that we’re seeing a legitimate maturation in approach from the 23 year old. And there’s nothing fluky in his BABIP or other batted ball indicators to warrant caution.

Verdict: Arenado’s offensive spike appears genuine, and this may be your last chance to try and acquire him at anything resembling fair return value.

Jon Jay, OF StL (.380/.470/.491, .425 wOBA, 9.0 BB%, 14.3 K% in 133 PA’s)

Jay has wrestled the centerfield starting gig away from Peter Bourjos with a torrid stretch over his last 40 games which has been driven by a rather staggering .433 BABIP and a 4% boost to his walk rate. The BABIP number is obviously unsustainable, however, and the walk rate gains have been more like a regression to last year’s norm than a sign of any newly developed skill. If we normalize his BABIP closer to his already-above-average .346 he quickly loses almost all of his shine, as his two homeruns and three steals during the stretch represent par for his course. Jay’s always had a solid-average hit tool, but given a league-average eye and lack of counting stat accumulation he only ever really brings value during stretches like this current one where balls are falling in at an even greater rate than usual. At 29 there’s really not much in the way of untapped upside here.

Verdict: While he’ll retain value in deep leagues as a steady contributor in AVG owners elsewhere who’ve benefitted from this run should seek to capitalize and shop him for any return value they can find early this off-season.

Tyler Flowers, C CHW (.289/.352/.553, .394 wOBA, 4.8 BB%, 32.8 K% in 125 PA’s)

I’ve long been hopeful for a breakout from Flowers, as despite a pretty terrible hit tool and approach he’s always shown just enough power potential to look like he might one day possibly maybe be interesting. Well, he’s certainly interesting now. He’s managed to overcome the absurd whiff and walk rates noted above and, with the help of an outsized .394 BABIP, turn into the second half’s third most valuable catcher. What’s interesting about Flowers is that while he’s a hyper-aggressive swinger he’s only nominally below-average at chasing balls out of the zone. And during this recent stretch he’s improved in that area enough to raise an eyebrow. That particular aspect of his second half is interesting from a narrative standpoint, as he became the latest in a long and storied line of begoggled Major Leaguers right around the turn of the second half.  There’s certainly not enough here to warrant buying in based on the convenient confluence of BABIP luck and new specs, but it’s something to file away.

Verdict: The discipline numbers remain atrocious and the BABIP is wholly unsustainable, meaning there’s no discernable reason to expect him to be more than the .217 hitter he’s been for his career going forward. For now chalk it up to a hot streak and move on, though take note of the power of the goggle when you’re trolling for a late-draft 2^nd catcher in AL-only leagues next spring.