In the now-delayed deal, the Twins acquired starting pitcher Kenta Maeda from the Dodgers in exchange for sending Graterol to the Red Sox. The surprising trade was announced Tuesday night, and Twins fans’ evaluation of the deal tended to vary depending on this very question: just how much upside does Graterol have?
The other side of the trade is easier to evaluate. Maeda’s talent is considerable, and his team-friendly contract makes him even more valuable. But as recently as a month ago, the assumption was that the 100-mph-throwing Graterol would begin the season in the minors as a starting pitcher, keeping him on the path of becoming a rotational ace.
That narrative was reversed when Twins coach Wes Johnson revealed that Graterol was preparing for a bullpen role a few weeks ago. Graterol served in that role in September and in the postseason for the Twins, but had been a starting pitcher to begin the season, before a shoulder impingement shelved him for three months.
If he started the season in a relief role, it was unlikely he would ever return to the starter role for two reasons. First, he was expected to have tremendous success as a late-inning reliever with a triple-digit fastball and a plus-plus slider. But he also had never made more than 19 starts as a pitcher in any year, or pitcher more than 102 innings. His arm had never shown it could withstand a starter’s workload.
“Value” is a tricky term, as it can mean a lot of things. The value to a team of a fire-throwing reliever versus a top-of-the-rotation starter can be debated. Because relievers are used more often, and especially because they are inserted into games in critical moments, they can impact more games in more meaningful ways than a starting pitcher. But starting pitchers pitch more innings, thus suppressing more runs.
Those two values are depicted differently by different statistics. Wins Over Replacement (WAR) values innings pitched, and starting pitchers lead relievers in it every year. But Win Probability Added (WPA) values how much a player increased the probability of their team winning a game. High-impact relievers often lead pitching staffs in that metric.
However, there is another meaning of value: rarity. It is usually harder to find starting pitchers than relievers. This has been especially true for the Twins, as their top-tier bullpen includes lots of reclamation projects, while they spent their offseason futilely begging “impact” starting pitchers to take their six-figure deals.
So when the Twins, who are hungry for impact pitching and flush with relief arms, decided to move potential ace Graterol to the bullpen, it probably should have told us something. It probably should have told the Red Sox something too. Apparently it is now, and it’s significant enough that it is jeopardizing their signature offseason deal, including shedding over $40M in payroll this year.