Spring Training games are in full swing, and yet, one of baseball's most impactful starters remains without a team.
Jacob Arrieta has been to the top of the pitching mountain, capturing the 2015 National League Cy Young Award with a summer that evoked Bob Gibson before helping the Cubs break the longest championship drought in professional sports. Arrieta has proven his ability and his mettle in the game's biggest moments, and his league-adjusted 151 ERA+ ranks third among starters who have thrown at least 500 innings over the past three seasons. It's a resume that would typically command a substantial contract in free agency, yet the righty does not seem to be generating much enthusiasm on the market.
Why have teams been slow to ink Arrieta? Below is an analytical look at reasons why MLB front offices are hesitant to commit to the former Cubs ace.
Velocity
This isn't surprising to those who watched Arrieta pitch the past season, but Arrieta's velocity might be the most concerning part of his profile. Below are Arrieta's dips over the past three seasons on each of his pitch types, per Statcast™ and pitch-tracking data:
Sinker (2015/ '16/ '17): 95.3 mph / 94.5 mph / 92.2 mph
Four-seam fastball: 95.1 mph / 94.2 mph / 92.1 mph
Curveball: 81.3 mph / 81.1 mph / 78.8 mph
Slider: 90.8 mph / 89.8 mph / 87.8 mph
Changeup: 89.5 mph / 89.2 mph / 87.3 mph

Arrieta essentially shelved his four-seamer last season, throwing it only 54 times after he'd averaged 629 in the prior two campaigns. That took away a pitch with a healthy 24.5 percent whiff-per-swing rate in 2015-16, as well as an offering he could tunnel alongside his changeup and breaking balls.
Arrieta's 25.7 percent whiff rate on all his pitches sat just outside the top 20 qualified MLB starters in '15 (min. 1,000 total swings induced), but slipped to 21.5 percent last season. Declining velocity is maybe the most obvious red flag for a free-agent pitcher, and it appears Arrieta will have to rely more on craft and command in the years ahead.

Contact allowed
Arrieta set the standard for missing barrels to go along with his career-high 206 strikeouts in 2015. Statcast™ considers a hard-hit ball to be one hit with a 95-mph exit velocity or greater, and Arrieta's 24.8 percent hard-hit rate in '15 is the second-lowest Statcast™ has tracked from any qualified starter over its first three years (Clayton Kershaw edged out Arrieta with a 24.5 percent rate that same season).
Arrieta was also fifth best at getting batters to "top" the ball, or drive it straight into the ground, doing so on 47.8 percent of the contact he allowed. Unfortunately, both rates declined over the past two seasons; the 32.2 percent hard-hit rate Arrieta allowed last year was essentially league average, and his topped-ball rate dipped all the way down to 35.7 percent.
The more discouraging development is that Arrieta is allowing more of the most damaging contact from hitters. Pitchers hope to avoid hard-hit balls, but they especially hope to avoid them in the air. Unfortunately for Arrieta, his rate of hard-hit line drives and fly balls allowed has climbed steadily over the first three seasons of Statcast™ data. So too has his barrel-per-batted ball rate, which measures the most ideal air balls for hitters based on their combinations of exit velocity and launch angle. More barrels inevitably mean more home runs, and Arrieta allowed a career-high 23 last summer.

Age
The biggest reason why Arrieta remains unsigned could be simply be his age -- a factor general managers have clearly become warier of when evaluating free agents. History isn't on Arrieta's side as he celebrates his 32nd birthday in March. Only four of the 29 pitchers to claim Cy Young Awards in the Wild Card Era (1995 - present) did so after their age-32 season: Roger Clemens (ages 34-35, 38 and 41), R.A. Dickey (37), Roy Halladay (33) and Randy Johnson (35-38). Four is also the number of pitchers aged 33 or older who claimed league ERA titles in that span (Kevin Brown, Chris Carpenter, Clemens and Johnson).
Those are high bars to set for any pitcher, but Arrieta's comparables are not encouraging, either. The five closest pitchers to Arrieta through age 31, per Baseball-Reference's similarity scores, are Pete Vuckovich, Clay Buchholz, Jordan Zimmermann, Pat Jarvis and Tim Belcher. Of those five, only Belcher pitched in the Majors past his age-33 season (Zimmermann has struggled with injuries and Buchholz is currently beside Arrieta on the free-agent market).
Belcher, Jarvis and Vuckovich combined for a 4.90 ERA from their age-32 seasons through the ends of their careers.
Arrieta's peak three seasons ago ranks among the greatest performances in baseball history. But his next team will be paying for the future, not the past, and the data suggests that zenith is likely in the rear-view mirror.
Arrieta still possesses the skill, guile and competitiveness to retire Major League hitters, but for how long? Teams may be wondering if Arrieta could truly fulfill the value of the megacontract he's seeking.