Ray Allen is one of the main reasons LeBron James won one of his two titles with the Miami Heat and made the Finals this past season. After winning a title with the Boston Celtics, Allen moved to South Beach and was a key part of Heat teams that emphasized spacing and shooting above all else.
The Heat, led by James, Chris Bosh and Dwyane Wade were a perfect fit for Allen. In his prime, Allen could do it all. His best skill was his shooting, but he could score off the dribble and finish inside. He was also serviceable on defense - not quite athletic enough to be elite but good enough to defend his man.
As Allen has aged, he's become reliant on his one elite skill: shooting. In his last few years with the Celtics and Heat, Allen followed the natural progression of athletes and started to decline as he approached 40. Now, at 39, he is nearly useless on defense, can't create his own shot and is best used as a small-ball lineup shooter where he could be hidden defensively.
That one skill coupled with his athletic decline makes him a player of us e for a handful of teams - one of which happens to be the Cleveland Cavaliers. And considering where the Cavs will be once the Kevin Love deal is official on August 23 (spoiler: the Cavs are going to be an elite team next season), Allen is the kind of comfort food player you want. Players who shoot 37.5 percent from three per 36 minutes at age 39 and can be signed for the minimum are the players you want to round out a title contending roster.
This is especially true with the Cavaliers having made several moves to acquire veteran three-and-D types this offseason. By signing both Mike Miller and Shawn Marion, the Cavs have reduced their need for Allen. While Marion isn't the same caliber of shooter and Miller doesn't quite have the reputation Allen does, both, even in their late thirties, can do more on the floor than Allen. They can defend opposing wings and Marion can defend fours for stretches as well. Miller is also, over their respective careers, a slightly better 3-pointer shooter than Allen.
Allen, at this best, can defend non-creators who can't threaten him off the dribble like the Spurs' Marco Belinelli. If Allen is matched in space with a Lance Stephenson-type, it's two points waiting to happen. In isolation last season, Allen gave up .98 points per possession per Synergy Sports. Miller allowed .9 points per possession in isolation with the Grizzlies, while Marion allowed .92 points per possession with Dallas and often defending the opposing team's best scorer.
This becomes even more complicated when you factor in Dion Waiters, the Cavs' enigmatic third year guard. Depending what your view on Waiters is, you either view him as a potential excellent fourth option with heaps of defensive potential or a inefficient knucklehead who has defensive potential. Either way, Waiters is going to be faster and stronger than Allen next season. He'll be able to attack the rim, create shots for other and with a few adjustments, can be an effective spot-up shooter when playing with James, Love and Kyrie Irving.
Allen can't create his own shot or finish inside anymore. The vast majority of his shots took place behind the 3-point line and while he did take a high number of shots near the rim, he shot at roughly league average rate. As he ages, and keeps losing steps, it's likely that Allen shot charts trend even more towards the perimeter.
This isn't to say the Cavs shouldn't try to sign Allen. His skill set is useful for a Cavs team that will have to play small and shoot threes well to maximize the roster's potential. He's also a better shooter than James Jones (another free agent signing) and can give the Cavs depth in case Miller or Marion goes down for an extended period, although Matthew Dellavedova and Joe Harris provide that same depth at a lower cost and relatively similar ability to Allen late in his career. But asking him to be anything beyond a shooter who provides depth would being unrealistic about where Allen is at in his career.