Editor's note: This article appears in the Dec. 18 issue of ESPN The Magazine.

Two summers ago in this space, I ranted about the phenomenon of "Tremendous Upside Potential" (TUP for short). Suddenly we were spending way too much time announcing the greatness of players who weren't close to great yet, predicting special things for raw rookies and trying to discover the next athlete who had a chance to be an all-timer. Everything was projection. Félix Hernandez wasn't the next Gooden, but he could be. Sidney Crosby wasn't the next Gretzky, but he could be. You get the idea.

Today I give you the bastard older brother of the TUP Guy. Introducing The Tantalizer. And if The Tantalizer sounds a little too much like a CBS midseason replacement drama starring Ray Liotta, so be it. Tantalizers are a bigger part of the sports scene than you may realize. Personally, I am overwhelmed by them, can't get away from them.

Everywhere I look, I'm being tantalized.

Tantalizers come in one of five forms:

1. A TUP Guy with a decent chance still to be very good or great. Even though it may make more sense for our team to trade him for immediate veteran help, we pray against it because we can't handle the possibility of being haunted down the road by the guy. Think Gerald Green.

2. Someone who's been around long enough for us to have embraced his TUP, digested it and digested it again ... and now we're just waiting for him to realize it. Only it's not quite happening. You don't want to get too concerned, but at the same time, you can't stop thinking: It's not happening, it's not happening, it's not happening. Think Shaun Livingston.

3. A prospect who can't reach his TUP because he keeps getting hurt, until we find ourselves saying, "Man, if he could only stay healthy, we might really have something here, only we're in denial, because he'll always be better at getting injured than actually becoming a go-to player." Think Al Jefferson.

4. An older TUP Guy who never lived up to his hype but has shown just enough over the years to make a breakout still seem conceivable, even though we have a staggering amount of evidence at our disposal that argues it's not in him. Think J.D. Drew.

5. A young star who reached much of his TUP before being derailed by injuries. Now he's battling his way back, and it's painfully obvious he's not the same, only we can't admit that, because he looks the same and he's too young to be past his prime, and if that's not enough, there's always a chance he could still spin the fairy-tale finish. Think Kerry Wood or Mark Prior.

I haven't followed the last two guys too closely, but as a Boston fan and an L.A. resident, I have extensive experience with the other four. I renewed my Clippers season tickets twice because of Livingston, a lanky point guard who sees the court like a young Magic and plays defense like a young Pippen. He couldn't be more tantalizing. At every home game, I find myself picking him apart like a figure skating judge; my standards are impossibly high. Then he'll make a play nobody else could make -- a rebound in traffic followed by a coast-to-coast drive and vicious dunk, or a one-handed laser through a sea of arms and hands that somehow finds Elton Brand for a layup -- and I'm chugging Livingston's TUP Kool-Aid again. Every time I hear a trade rumor of the Cuttino Mobley-and-Livingston-for-Ray Allen variety, I nearly have a heart attack. What? Trade Livingston?!? He's the next Magic! Two nights later, I'll watch him stink up the joint and think: Ray Allen? Could they even get Allan Ray for him?

It's a cruel merry-go-round the Tantalizers run, but that's what happens when you allow teenagers into pro sports leagues. At least Livingston shows some flashes. Jefferson and Green haven't done squat. Jefferson has nimble feet, impossibly soft hands and a nose for rebounds, three prerequisites for any future All-Star big man. It's easy to imagine him becoming a 25/12 guy some day -- of course, his hoops IQ needs to double for this to happen. Green possesses a gorgeous, jaw-dropping jump shot and leaps higher than a border collie in a Frisbee-catching contest. It's easy to imagine him becoming a cross between T-Mac and George Gervin, even when he's running around like a decapitated chicken, which is almost all of the time.

Will they ever make it? Impossible to say. I've watched nearly every minute of every professional game they've played ... and I have no clue. None. Still, when there were rumors that both were headed to Philly for Allen Iverson last summer, many Celtics fans reacted as if we were about to give up the Bunker Hill Monument and Fenway Park. And I was one of them. Wait, we're trading Big Al and Gerald? They're potential franchise guys! We can't give them both up! I don't care if Iverson is one of the 40 best players of all time and still in his prime! This is crazy! That's the thing about Tantalizers: You tend to throw logic out the window when they're involved.

It's not just us fans. When the Sox started to court Drew a month ago in the face of overwhelmingly poor feedback from every fan base that ever supported him, you could almost hear the members of the front office talking themselves into the deal. "His beautiful left-handed swing would look perfect in Fenway, right? We need a good defensive outfielder, and he's one of the better ones, right? We love OPS guys, and he's always in the 900s, right?" (Wait, here comes the catch ... ) "Sure, he's missed 292 games in the past seven seasons, but if he can just stay healthy and motivated, he's an All-Star!" Like there's a great track record with keeping often-injured, mercurial athletes healthy and motivated by throwing $14 million a year at them.

That's the rub with Tantalizers: You never know. When I was still living in Boston in 2001, the Celtics had a rookie swingman who looked totally lost, was terrified to shoot and played softer than a prevent defense. For prolonged stretches of games, you forgot he was out there; he'd just disappear into thin air for three or four minutes at a time. By February, the Celts realized they had a chance to compete in a crummy Eastern Conference, so they cut their losses and traded him for bench help. At the time, my father and I were fine with it. We thought Joe Johnson was just a Tantalizer who would never actually amount to anything.

Five years later, he's carrying a decent Hawks team and seems like a lock for the All-Star Game. You never know. You really don't. Tantalizers can break your heart or come through when you least expect it. There's no rhyme or reason to it. By the end of this decade, Livingston really could be the next Magic, Jefferson really could be a franchise forward, Green really could be the new Iceman and Drew really could be a back-to-back MVP hitting behind Big Papi. There's probably no way all of these things will happen, but you have to admit ... the thought is pretty tantalizing.

Bill Simmons is a columnist for Page 2 and ESPN The Magazine. His book "Now I Can Die In Peace is available on Amazon.com and in bookstores everywhere.