There seems to be three standard arguments against trading Coco Crisp to Boston:
1. The Indians don't have anyone to replace his (offensive, speed) production in the lineup
2. Andy Marte isn't going to pan out
3. The Indians won't be able to replace his defense in the outfield
And there seem to be three standard arguments for trading him:
1. The Indians need to sell high on Crisp (he won't continue to be this good)
2. Crisp doesn't provide enough production for a left fielder
3. Crisp is a good player, but Marte is worth it
I tend to fall into AF #3, provided the Indians address both AA #1 and #3.
Let's address AF #1 before I go any further. To do that, I looked at Crisp's 10 most similar batters through age 25. Since the Indians control him through the next four seasons, I looked at the similar batters' age 26-29 seasons.
UPDATE: The numbers in the chart are Wins Above Replacement, adjusted for era.
Most of the similars had pretty good careers. Lou Brock is the lone Hall of Famer on this list, but several others would make the Hall of Very Good, if there was one. Only one of the players on this list (Garvey) made a significant improvement after the age of 25, and four saw their careers take a nosedive:
Roy Weatherley. Indians outfielder who slugged .464 in 1940 (his age 25 season) and didn't come close to those power numbers again. He was undersized (5'6", 170 lbs.)
Tito Francona. Another Indians outfielder who (again) had his career season at age 25 and didn't come close to repeating it. Similar size and weight to Crisp (5'11", 190 lbs.)
Don Mueller. New York Giants outfielder with little speed. Named "Mandrake the Magician" because of his ability to accumulate seeing-eye singles.
Ron Northey. Slow-footed outfielder who had an exceptional arm. He was done as a full-time player after 1947, although he hung around as a pinch-hitter until 1957.
So what about those who kept their production at their age-25 levels?
Lou Brock. Hall of Famer; held the all-time stolen base mark until Rickey Henderson topped it. Didn't hit for much power after turning 31, but was still a .300 hitter well into his late 30s.
Garret Anderson. Current Angels outfielder who developed into a power threat as he got older. Has lost some power in the past couple years, but is still hitting for a high average.
Lenny Dykstra. "Nails" was an on-base machine, posting a career .285/.375/.419 line. Never hit for that much power, but compensated with a good eye at the plate and good speed. A back injury forced him to retire at age 33.
Now, for the other three on the list:Steve Garvey. The only non-outfielder on the list, Garvey was a mainstay for the Dodgers through 1970s and early 1980s. Very durable and consistent player.
Dom DiMaggio. "The Little Professor" missed three seasons due to World War II. After he returned, he picked up where he left off. DiMaggio made up for Ted Williams' defensive shortcomings in left with his good range in center field.
Amos Otis. He wasn't quite as good after age 25, but he was still a valuable contributor to several good Royals teams in the 1970s and 1980s. The center fielder was a good basestealer and had good power.
For the most part, Crisp's comps look pretty good. Five of the top six similars had long distinguished careers. Two of the four rapid decliners didn't have much speed.
To me, Crisp is most valuable as a center fielder, although he provides enough defense and power to justify a corner spot. With Grady Sizemore, a better defender, already entrenched in center, Crisp isn't as valuable to the Indians as he would be to a team without another option in center field. This is a situation where the Indians don't really need to move him (especially given the lack of corner bats), but could move him given the right return.