Hard-hit rate sign that Mets' Smith will improve

Dominic Smith and Amed Rosario's sophomore seasons are getting closer by the day, and it's an important year for the two young Mets infielders. They've now moved past their "prospect" status, and 2018 is the next step in what New York hopes will be their development into franchise cornerstones.
Smith, especially, has something to prove. The 22-year-old did hit nine homers in his first 49 big league games, which is promising, but he paired it with a disappointing .198/.262/.395 slash line.
As of now, the Mets' starting first-base job is Smith's to win. And if he does win the job in Spring Training, there are some signs that he could run with it. Several key Statcast™ metrics indicate that Smith's stat line could be significantly better in 2018.

Start with his expected weighted on-base average. Smith's wOBA -- a measure of overall offensive production, similar to on-base percentage but with each outcome weighted for its value (e.g. a home run is worth more than a single) -- was just .285 in 2017. That's far below the Major League average wOBA of .327.
But Statcast™ can take a player's quality of contact, using the exit velocity and launch angle of each batted ball, and generate an expected wOBA. Smith's xwOBA was .324, indicating that he was essentially league average going by contact quality. The 39-point gap between his expected wOBA and his actual wOBA was the ninth largest of 428 hitters who had at least 100 at-bats last year. Given Smith's young age and high prospect status, an improvement next season is well within the realm of possibility. With similar contact quality and better results to match, he could be looking at at least solid production in 2018.
Of course, there's no guarantee that Smith's results in the box score will automatically match up with the quality of contact. There is one main mitigating factor, which is that Smith is a slow left-handed hitter; he won't beat out infield hits, and if he hits a ball into the shift -- even if he hits it well -- it's an out. Hard outs into the shift will suppress a player's wOBA relative to his xwOBA.

But a lot of Smith's hard-hit outs in 2017 weren't shift groundouts; they were in the air. Half of Smith's hard-hit outs, 13 of 26, were fly balls or line drives. (Statcast™ defines a hard-hit ball as having an exit velocity of 95 mph or higher.) Hard-hit air balls are the most likely to do damage, so it's better for Smith to have outs like those than a ton of hard-hit outs on the ground. In better circumstances, a hard-hit flyout or lineout might be a double or a homer.

Smith also had an excellent hard-hit rate overall: 42.0 percent of Smith's batted balls last season exceeded Statcast™'s 95-mph threshold. Of 387 players with at least 100 batted balls in 2017, Smith's hard-hit rate ranked 52nd -- coincidentally, just above former Met Daniel Murphy -- putting him inside the top 15 percent of hitters.
Yet fewer than half of Smith's hard-hit balls, 46.0 percent, actually yielded base hits. That was the 13th-lowest rate among 317 hitters with at least 50 hard-hit balls last season. Smith's .469 batting average on hard-hit balls was nearly 100 points lower than the overall MLB average, which was .558 on all batted balls hit 95-plus mph in 2017. If Smith could keep up his rate of hard contact over the course of a season, it seems likely he'd be standing on base more often than he was in 2017, and that's what the Mets are hoping for.