Free agent Arrieta presents dilemma for suitors

A late bloomer to superstardom, Jake Arrieta has hit free agency ahead of his age-32 season. His story has been well-chronicled -- a fringe pitcher who was nearly out of the game resurrected his career in Chicago -- and his next chapter is waiting to be written.

Arrieta, who won the 2015 National League Cy Young Award, is arguably the top starting pitcher on the market, though his age and topsy-turvy 2017 performance could present a further dilemma to interested suitors. Is he an ace who could put a contender over the top, or is he more of the enigma we saw in 2017? With some help from Statcast™, let's break it down.

Hard-hit rate

In 2015, when his value was at its peak, Arrieta was nearly unhittable. The right-hander led MLB with a .185 opponents' batting average, struck out a career-high 236 and gave up just 10 homers, second-fewest among those who qualified for the ERA title.

A look at the quality of contact against Arrieta reveals that even when batters were making contact against him, it was incredibly weak contact. He gave up hits with an exit velocity of 95 mph or higher -- classified by Statcast™ as hard-hit -- on just 24.8 percent of his total batted balls. That's the second-lowest mark by a starter with at least 300 batted balls against him in a season since 2015.

His hard-hit rate crept to a still-respectable 29.8 percent in '16, 12th-best in the Majors, but spiked to 33.4 percent in '17, which ranked 62nd of 128 MLB pitchers with at least 300 batted balls. Each of the career-high 23 homers he gave up in '17 were at an exit velocity of 95 mph or higher.

While there were a record 6,105 home runs in 2017, MLB's collective hard-hit rate was 33.3 percent, a tick under Arrieta's showing, and was actually lower than in '15 (33.5 percent). The significant drop-off here could be cause for concern, as we'll examine next.

Pitching to contact

Arrieta saw a significant dip in his overall velocity -- from 95 to 92 mph on his fastballs from '15 to '17 -- and history suggests most mid-30s pitchers don't regain that velocity. He might have to alter his approach, and given that his strikeout numbers have dropped in sync, that could mean pitching to contact more often.

A telling metric here would be "topped" balls, those hit directly into the ground. Arrieta was once one of the game's best at generating such contact, but that rate has dropped substantially, from 47.8 percent in '15 to 43 percent in '16 to 34.7 percent in '17. Couple his elevating hard-hit rate with this dip in topped balls and there might be pause over his sustainability with this specialty.

Command

If Arrieta does alter his approach, he might need to establish better command of the strike zone. A look at his heat maps the past three seasons reveal that he has steadily thrown more up and over the middle, which are more favorable quadrants to hitters.

Arrieta also wasn't as sharp on the edges as he had been the two years prior. Looking at Statcast™'s detailed zone metric, when Arrieta threw borderline pitches, they were called balls 28.9 percent of the time, the 13th-highest rate of 118 pitchers who threw at least 750 borderline pitches.

Of course, strike zones are subjective based on umpire and other situational circumstances, but Arrieta's high ball rate here may explain why he walked roughly eight percent of all the batters he faced, a big increase from his 5.5-percent rate in 2015.

Put-away pitches

Looking at a positive, when Arrieta goes deep into counts, he is among the elite in generating outs, doing so on 38 percent of his total two-strike pitches in '17. That ranked 17th among 130 pitchers who threw at least 500 two-strike pitches. He also got 48 punchouts via called third strike, including 37 on his sinker, third-most in MLB in '17.

In turn, these figures bode well because Arrieta was also highly successful early in counts. On the first pitch, batters hit .262 against him, the game's eighth-lowest rate (minimum 50 at-bats).

Pitching arsenal

Perhaps one of Arrieta's most appealing aspects is his well-rounded repertoire. With one of the game's most animated cross-body motions, which creates even more deception, Arrieta throws a four-seamer, sinker, curveball, changeup and a slider-cutter combo that offers disruptive movement.

He turns to his sinker most, and almost nobody has thrown the pitch better. Batters have just a .304 weighted on-base average against it, fourth-best among 174 starters who have had at least 100 at-bats end on a sinker or two-seamer (which has similar movement). wOBA is a version of on-base percentage that accounts for how a player reached base, putting more value over a home run than a walk, and the league-average wOBA was .327 in '17 on all pitches. Arrieta surrendered a .320 wOBA on his sinker last year, 17th-best (minimum 75 at-bats).

Similar figures are reflected in his sweeping curveball. Since '15, Arrieta has surrendered a .201 wOBA against the pitch, seventh-lowest (minimum 150 at-bats), and in '17, he gave up a .252 mark.

Depending on how you look at Arrieta, you can see the 2015 Cy Young Award form is still present in Arrieta, but his 2017 performance might weigh more heavily on the eyes of suitors. He offers the most feast-or-famine probability of any other free agent.