We know that the Celtics were a better defensive team with a healthy Avery Bradley on the court than Ray Allen (healthy or not). Interestingly, per this study on 5 man units done by Celtics Town, it seems that the Celtics were better offensively as well.
Ray v. Avery: A Study in 5-Man Units | Celtics Town | Boston Celtics blog | Celtics news
Defensively, we shouldn’t be very surprised by these results. Bradley is a better individual defender than even a healthy Allen, and the Allen we saw in the late regular season/playoffs was far from healthy. But the offensive differential doesn’t line up with the standard narrative. It also, quite honestly, doesn’t match up to standard logic. Despite Bradley’s obvious improvements offensively and Allen’s notable aging, we would have expected the better offensive lineup to be the one with the better offensive player. Allen was clearly still better offensively than Bradley. Ray had a higher PER, a better eFG%, and a lower turnover percentage (turnovers per 100 possessions). So what do these numbers mean? Is it possible that Boston’s offense simply didn’t need to play Allen to be efficient? Actually…yes. Yes it is.
Check the link for the full context, but it is an interesting finding. I do think you have to account somewhat for Ray's battles with injuries, but in terms of moving forward, that may or may not be an issue for the rest of his career.
This isn't meant to be yet another pile-on of Ray Allen. He was the first option on Danny's shooting guard list and we would have been very good with him back in the lineup. But the point here is, we're not necessarily going to be worse without him, and there's a good argument for us being better.