1. Almost any closer is good enough to close games at a 70-80% rate.
2. It is better to have an effective middling starter than an effective middling closer.
3. Relievers almost always "find" an extra few mph on their fastballs because they need not save their stuff for later in the game.
4. It is a fools' errand to spend real money on a closer unless said closer saves games at a 88% rate or better.
5. In the history of baseball, failed, faded, stuff-starved, or older starters often find remarkable success as closers, as evidenced by Dennis Eckersley, Rick Aguilera, Mudcat Grant, Jason Isringhausen, and, of course, Mariano Rivera.
1. Arroyo is a sunk cost and cannot be traded.
2. The Reds will have at least five starting candidates likely to perform better than Arroyo, in Cueto, Bailey, Wood, Leake, Volquez, Willis, perhaps Chapman, and others that may be acquired.
The move of Arroyo to closer would open the door for Chapman to be groomed as a starter.
3. Arroyo's control would assure that few runners get on base via the walk.
4. Arroyo's unorthodox pitching sequence, arm slot, and offerings would be difficult to hit, especially after facing "stuff" pitchers all game. (Of which the Reds have many)
5. Arroyo has an arm that is made for logging innings. This likely means he could handle the stress of pitching multiple days in a row.
6. Arroyo has the experience and mindset to be unflappable in tight situations, which should mean he'd be good at forgetting poor nights.