You never appreciate greatness until it is gone.

It's human nature. Being caught up in the moment is what comes natural to the majority of us as we understand context, but do not always apply it. It's all over this world. Do you appreciate your friends when they are there? Or do you only realize the value of their presence when they are gone?

Most of us tend towards the latter. At least I know I do.

It is easier to place context on something when you are not emotionally involved or too close physically. This can be a problem for the average fan who invests his heart and soul in a team. For fans of the Boston Celtics, context is even more difficult to consider because of their glorious past.

The Celtics history is full of superstars from Bill Russell, to Larry Bird, to Paul Pierce.

Playing in the shadows of Bird and Russell hasn't affected Pierce. This year he surpassed Larry Bird to become the team's second highest scorer of all-time. Pierce is 34 years of age but isn't slowing down the way most veteran scorers at his age do. He may not be at his best right now, but throughout the regular season he carried the Celtics when they needed him most.

Right now, the team is being carried by Kevin Garnett. Garnett is even older than Pierce and plays a tougher position. Garnett has just turned 36 and is now the Celtics' center. Most forwards at 36 years of age are stumbling around the court playing minimal minutes like a Jamaal Magloire or can barely move under their own weight like a Shaquile O'Neal.

Despite suffering a torn ACL only a matter of a few seasons ago, Garnett has bounced back and prolonged his career under difficult circumstances. In his prime with the Celtics he had a defensive star, Kendrick Perkins playing center to ease his workload. Brandon Bass is a good power forward, but there is no doubt that Garnett's body has to endure a lot more as the team's starting center these days.

Garnett may not be breaking any records this year like Pierce, but the third of the big three, Ray Allen, became the team's all-time leading three point scorer as recently as a year ago. Allen may be on the bench these days, acting as the sixth man, but he is still giving the Celtics quality minutes as a 36 year old shooting guard.

When the Celtics acquired Allen all those years ago, they added a talented scorer to their roster. There are plenty of talented scorers in the league, but there are none who are as dedicated as Allen. His determination to refine his game, even when he is already an expert at what he does, is phenomenal as he is constantly in the gym throwing up jumpers.

Shooting is one thing, but Allen's commitment to keeping his body in excellent shape is amazing also. Despite his age, he is still more often than not the fittest player on the court and there is no talk of him having to retire after the season despite his contract being up.

It's not only the big three who need to be put into context however.

The team's leading star right now is a 21st overall draft pick out of Kentucky in 2006 who was acquired in a trade with the Phoenix Suns. That pick was acquired for a pick that ultimately turned into Rudy Fernandez as well as some cash considerations.

It's not very often that a pick that late in a draft, acquired for so little, turns into one of the most productive point guards in the NBA. Of course, the 21st overall pick in 2006 was Rajon Rondo. Of course finding a star like Rondo at that stage in the draft has some element of luck to it, but it is also a testament to the management which runs the Celtics organization.

With the Celtics in the second round of the playoffs, on the verge of another Eastern Conference playoffs, and no crippling cash commited to contracts for the future, one must sit back and appreciate just how fortunate Celtics fans are.

Of course because of their history, it is hard for Celtics fans to appreciate anything less than championship successes. Those are the standards that Boston basketball lives by. It is also a major reason why the team reaches the heights it does year in and year out.

Some franchises can go decades without even an appearance in the first round of their respective playoffs across all sports. For the Celtics, this trip towards championship contention needs to be put in that context for it to really be appreciated.