When considering a legitimate prospect, it’s important not to judge him on his first few plate appearances, perhaps even his first hundred. Ty Cobb, who would hit .366 for his career, batted .240 as a frightened rookie. Mickey Mantle had to be sent down in 1951, and Willie Mays begged Leo Durocher to send him down that same year. A rush to judgment would have short-circuited three legendary careers. It didn’t happen with these three, but it has happened – and because these never-weres went away silently, neither they nor we will ever know what they would have accomplished, what we missed the chance to see.

Having patience is especially important when it comes to Yankees prospects because the organization produces so few of them. Since the brief flowering of the farm system that resulted in the core of the great Joe Torre-era teams – Derek Jeter, Jorge Posada, Andy Pettitte – the Yankees have had to rely almost exclusively on mercenaries to staff out their roster. This has led to some regrettable decisions, like Jaret Wright and Carl Pavano, to name recent examples, as well as a payroll so high that the Yankees have lacked the flexibility to fix their mistakes with an in-season trade. The reliance on the old and slow has also had an obvious, deleterious effect on team speed and defense.

If Hideki Matsui’s injury can be said to have a silver lining, it’s that the Yankees get a chance to inspect Melky Cabrera, one of their few (if not only) major league-ready prospects (last year’s draft produced a number of interesting future Yankees, especially future leadoff hitter Brett Gardner, but he and his contemporaries are still a long way from the Bronx).

Last year Cabrera had a very mixed season, even in the minors. He had extreme hot and freezing cold streaks, and at 20 it seemed unlikely he would be ready for the majors after just a brief trial at Triple-A. The Yankees, having punted on Carlos Beltran in the off-season, found themselves stuck with the aging husk of Bernie Williams in center field. They were surprised to discover that players that haven’t hit or fielded well since their early 30s don’t improve as they reach their late 30s. A desperate call for help went out and Cabrera was the desperate answer.

Today’s Cabrera is not the same player who was a failed experiment a year ago. Despite a few early misplays, he’s shown good range in the field and gunned down five runners with what looks to be a terrific arm. Unlike last season, when he failed to excel at Columbus, he opened this season hot and stayed hot, leaving Ohio with terrific .385 AVG/.430 OBA/.566 SLG rates. Last season’s intimidated Cabrera swung at nearly everything that came his way at the plate, seeing only 2.6 pitches per plate appearance. This season Cabrera has looked at 3.8 pitches per plate appearance, and the result has been seven walks in 63 plate appearances, a better rate than he had shown in the minors.

The only troubling aspect of the new model Cabrera has been his lack of power.With 16 hits so far, he’s managed just two doubles, no triples, and no home runs. Cabrera is not the new Otis Nixon (not just the epitome of speed without pop but a Yankee farmhand a million years ago), and some power should manifest itself with more playing time.

Still, power will never be the major component of Cabrera’s offensive game. He is still so young and unfinished that it is difficult to imagine just what his mature numbers will look like, but it seems most likely that he will be the same style of player that Bernie Williams was, though not as good: if Cabrera is to be a regular, he’ll hit for decent batting averages and middling power with an above-average walk rate. Shannon Stewart would be another broadly similar player.

That version of Cabrera is in the hazy future and may never come. For right now, it’s clear that the outfielder is helping the Yankees avoid falling to replacement level at two positions (anywhere Terrence Long plays is the other), but if the power doesn’t come this year it won’t be by very much. While on base percentage is the sine qua non of offense, slugging percentage, the ability to move runners around the bases and place one’s self in scoring position, is a close second. With his .371 on-base percentage, Cabrera has been good at the former but has neglected the latter.

While today’s game boasts the occasional good-field/no-hit center fielder, corner outfielders who slug .327 died off in the deadball era. Cabrera’s current home in left field has seen its defensive importance de-emphasized over the decades; teams have felt comfortable using left as a place to stash sluggardly sluggers like Ralph Kiner,Harmon Killebrew,Greg Luzinski,Pete Incaviglia,and Manny Ramirez.Teams have come to expect a certain amount of power production from the position, so relative to the league the Yankees aren’t receiving much production.

In the absence of other options, Cabrera is still making a valuable contribution, but as long as he continues to hit like a slow Scott Podsednik, his performance shouldn’t inhibit the Yankees from making a trade for a more rounded player. As a rule of thumb, the Yankees would bleed offense were Terrence Long to be the everyday left fielder. With Cabrera they’re confidently treading water and might still win. With Bobby Abreu, the position would be back in the asset column.

With only 55 at bats so far, it’s still a bit early, though, to decide that with Cabrera what you see is what you get. Just a little bit of pop would go a long way towards turning his average and on-base percentages into major advantages. No one is saying that Cabrera will turn into a Cobb, Mantle, or Mays, but the lessons derived from their experiences – patience has its rewards – applies to him as well.

Mr. Goldman writes the Pinstriped Bible for www.yesnetwork.com and is the author of “Forging Genius,” a biography of Casey Stengel.