Tony Allen. Taking Celtics fans to hell and back.

The fact that I’m even writing this piece speaks to how far he came. If Tony Allen had left after last season, my reaction would have been no more than five words: “Good riddance, and thank God.”

But he didn’t leave after last season, then spent the most recent campaign completely re-inventing himself as a reliable player who almost seemed to know what he was doing when he stepped on a basketball court. He worked hard, defended the opposing team’s top perimeter player every night, and even limited some of his ill-advised plays. Those plays, as Bill Simmons tweeteth, helped make Tony Allen one of the most frustrating Celtics of all time.

But he transformed himself in the past year, to the point that he almost became one of my favorites. I still didn’t fully trust him in big situations (any situations?), but I came to admire the dogged way with which he played basketball. The unlimited pursuit of the opponent’s best player. The willingness to play his role, whether it be as a benched towel-waver, the second team’s lead guard, or simply spelling minutes for Ray Allen and Paul Pierce. The enthusiastic reactions to Celtics runs, even when he was on the bench. It would have been hard to imagine last year, and it still feels odd to this day, but I actually liked Tony this year. I almost – almost – trusted him. And almost trusting TA was like almost trusting the girlfriend who has cheated on you 15 times: Considering where he came from, that’s one hell of a feat.

It’s weird: You finally learn to like a guy and he takes off. And believe me, I used to despise the way Tony Allen played basketball. I truly loathed his game, probably more than any other Celtic in my lifetime. There have been many bad players in my lifetime (I guess that’s what happens when you live through the worst Celtics era in history) but none of them have been as destructive as Tony Allen. He wasn’t the worst Celtic player ever, not by any means, but he had a devastating combination of just enough skills, just enough talent, just enough potential and way too much boneheadedness. His skills got him on the court and that boneheadedness, that unique ability to not only make the worst possible play but also make it at the worst possible time, kept him thoroughly in the doghouse of Celtic fans everywhere.

Tony was bad enough during the past couple years that some fans called for him to be cut before this season. The thinking was that it would have been better to pay him to leave the club and at the same time open a roster spot than it was going to be to have him on the team. That was how low TA was in our minds until, as you all know, TA suddenly became Good Tony Allen far more consistently than Bad Tony Allen, supplanting Marquis Daniels as the reliable bench player the Celtics needed and at the same time endearing himself to Celtic fans everywhere.

We’d always known Tony possessed unique talents that could have made him one of the league’s best reserves. He’d showcased his skills by being one of the C’s one bright spots during the miserable 2006-2007 season. But those talents had simply been overshadowed by all his shortcomings. I guess that’s what happens when you have legendary meltdowns often enough to have the phrase “Bad Tony Allen” coined, when you get injured every time you start to build any momentum. When his brain farts began to slow down, though, and his health allowed him to play, Tony’s positive impact was finally highlighted. Is there any other team in the league that can put a sub in and then see its defense on Kobe Bryant improve? I doubt it. Tony finally learned his role as a finisher and defender, stopped shooting his broken down jump shot as often, limited his dumbass (sorry, there’s no other word for it) turnovers and proved his worth as a sixth or seventh man. In the process we came to, if not like him or love him, at least appreciate him.

And now he’s gone. I won’t shed tears at his departure, but the fact that I even care about it speaks volumes to his improvements. The Celtics will actually miss Tony Allen, and those are a few words I’d never thought I would type. At this point, all I can hope is that Danny Ainge has a master plan to find some perimeter bench help. Otherwise, letting Tony Allen go is pretty inexcusable.

Because he would have helped next year. Improbably, against all odds, Tony Allen became a solid option. He rose from deep within the doghouse to become an almost-trusted performer, and in the process changed a whole lot of minds.

Mine included.