When the Mets traded top pitching prospect Scott Kazmir last month, one of the justifications they offered was that he was at least three years from being effective at the major league level. The Tampa Bay Devil Rays obviously disagree, as last night Kazmir became just the 29th 20-year-old left hander to start a game in the major leagues since the pitcher’s mound was raised in 1969.

He could have given up 10 runs without getting an out and he would have been doing more for his team than the man for whom he was traded, Victor Zambrano – it’s hard to help the team when you’re on the disabled list.

The question of injury is one that hangs heavy over Kazmir. Not just small for a ballplayer, but small for his age, he’s almost certain to be injured at some point. His violent delivery, in which he whips his leading leg and leaves his elbow open, looks to put incredible stress on his right hip and his throwing shoulder. With his frame, he’ll need a much cleaner delivery to distribute the force generated by his pitches if he’s to avoid injury.

Still, he’s got a very good shot at being a great pitcher. Last night he showed that the hype is deserved. He has absolutely incredible stuff – a riding fastball that hits 95, a breaking ball in the mid-80s, and an adequate change-up – and keeps the ball low and on the corners of the plate.

Hitters the caliber of Edgar Martinez and Ichiro Suzuki looked baffled by Kazmir’s outside fastballs and low-breaking slider. He worked too deep into counts and got into several jams, but showed composure in working out of them.

Beside the talent Kazmir showed last night, history is on his side as well. Since 1969, 12 20-year-old left-handed pitchers have had seasons in which they started at least five games and totaled at least 30 innings in the major leagues. There are three Cy Young winners among them, and two of the most coveted young pitchers in the game, Cleveland’s C.C. Sabathia and Pittsburgh’s Oliver Perez.

With the exception of Bruce Robbins, who pitched in two seasons for the Detroit Tigers and was never heard from again, and Rick Ankiel, whose emotional and psychological issues extend beyond anything a baseball club can be expected to solve, every one of these pitchers had a substantial major league career. With the exception of Kevin Kobel they all had (or in Perez’s case, are in the midst of) seasons where they were among the best pitchers in their league.

This isn’t terribly surprising; pitchers good enough to make the majors at 20 do so because of extraordinary talent.

The other thing these pitchers have in common is injury. Vida Blue, Frank Tanana, Fernando Valenzuela, and Steve Avery were all injured in their mid-20s. Some of them came back to have excellent careers; some just hung on. But in every case they were diverted from a Hall of Fame career path. Don Gullett, an extraordinary pitcher with Cincinnati’s Big Red Machine in the 1970s, never pitched after he was 27.

With the exceptions of the still-active Perez and Sabathia, every other pitcher on the list had arm troubles that cost them at least some of their early promise, and Kazmir’s a good bet to join them.

That is the risk. The reward is obvious – unless Kazmir flames out, like Ankiel, in an utterly unpredictable fashion, history suggests that at worst he will pitch 1,000 or more innings in his career with a season or two among the best in the league. That doesn’t live up to the hype Mets fans placed on him since he was drafted, but it’s incredibly rare. If he does better than that and has a career like Vida Blue, he’ll rank among the top 150 or so pitchers to ever live.

The Mets, so focused on the likelihood that injury will rob Kazmir of his chance to be Tom Glavine, missed the fact that even with that injury there’s a good chance he’ll be a Don Gullett.

This emphasis on risk at the expense of reward, and the concomitant dismissal of great potential because it isn’t the greatest of all possible potential, is a signal trait of a bad organization. Good organizations focus on what players can do and become, not what they can’t do and won’t become.

Last night Scott Kazmir began his major league career, pitching in front of one of the two brightest position prospects in the game, shortstop B.J. Upton. He could as easily have started his career in front of the other, David Wright, and it is to the Mets’ shame that he did not.