Ken Rosenthal talked to a rival scout about the chance of Cincinnati Reds lefty Aroldis Chapman joining the starting rotation, and the scout wasn’t exactly a fan of the transition:
“I hope they do start him, but they’re crazy if they do,” said the scout, who works for another National League club. “It’s Joba Chamberlain all over again.
“His velocity dropped off in the second inning. He couldn’t get his off-speed stuff over the plate consistently. No question in my mind, he’s the closer.”
Chapman averaged 97.7 MPH on his fastball last season, the second-fastest among all relievers, trailing only Kelvin Herrera of the Kansas City Royals (98.5). He finished the year with a 1.51 ERA and 38 saves in 71.2 innings of work.
The scout is referencing the Yankees pitcher who bounced between the bullpen and the rotation since making his Major League debut in 2007. The Yankees went to great lengths to protect his arm, which led to the moniker “Joba Rules” for their refusal to use him on consecutive days.
Though a closer more often than not pitches in some of the most important situations during a game, it is hard to overcome the value of pitching 175-200 innings. John Smoltz, a common point of comparison for starters-turned-relievers or relievers-turned-starters, posted 1.1, 3.2, and 2.2 Wins Above Replacement as a reliever between 2002-04 according to Baseball Reference. Despite the aggregate 2.47 ERA and 144 saves, his best season as a reliever (2003) ranks as his 12th-best season by WAR.
Chapman would have to become more or less average as a starter for the Reds to lose value moving him to the rotation. The average National League starter posted a 4.04 ERA last season.