It's obviously David Haye who has inspired this thread, but I don't want it to be about him, but rather fighters in general across the generations. Can a fighter come back after years of inactivity and 'physically' be as sharp as they once was? Or is this something that maybe only heavyweights can do/get away with? As I personally don't believe the lower weights can. And does age also play a factor, as in, would it make much difference whether the fighter is 28 or 38?
I think with regular sparring and training during the inactivity it would be possible. After a complete break probably not. Trying to think of some examples but then again you don't know whether they trained during their spell out.
I think with a certain type of fighter it is, but most stop fighting because there not motivated anymore, or have lost the drive, once you lose that then you'll never get back anywhere. That's why so many comebacks don't work out, majority of the time the fighter is just coming back purely for the money, as we all know you don't need to be the best to get money fights.
It seems to be a mixed bag on the successes and failures of comebacks, but like what as already been said, maintaining fitness and sparring sessions will certainly help. I bet Mayweather Jn continued (and continues) to train hard during his 1st retirement but he didn't have that long out the game. On the opposite side of the scale, there's no way Ricky Hatton would have looked after himself during his retirement. Thanks for the replies to the thread.