I'm not too big on accusing guys of doping based on how different they looked back when they were 21, it's pretty common for a person's body to continue developing past the age of 21.
I'd think if anyone, especially a prominent player, was on something while playing in Boston or New York, there would at least be whispers simply because of the fishbowl markets those two are. Some have whispered Damon simply because of how he's broken down in the past couple of years but look at how he played in Boston, it isn't that surprising.