As Carl Pavano trades pinstripes for sutures and the drumbeat for a Jason Giambi trade grows, it’s important to be clear on the difference between these two Yankees free-agent signings. Pavano should never have been signed. His resume showed neither health nor consistent success, and there was a high likelihood the Yankees would come to regret the signing. Conversely, Giambi was a good signing who has worked out fairly well for New York. He’s no longer the player who won the 2000 MVP award, nor is he a poster boy for speedy baserunning, good grooming, or fielding excellence. You wouldn’t hire him to teach a course in ethics, but the Yankees signed him to hit and hit he has.

If the Yankees fail to make the postseason this year, Pavano could prove to be general manager Brian Cashman’s Waterloo — a development that has all the marks of classic tragedy because it was an obvious and avoidable mistake. Pavano was 29 entering the 2005 season. He had thrown 200 innings in a season just twice: once in 2003, when his 4.30 ERA was actually below the National League average, and in 2004, during a fool’s gold season that convinced Cashman and the Yankees front office that Pavano, along with Jaret Wright, would be the team’s salvation from the failures of Javier Vazquez, Kevin Brown, and Jose Contreras.

Pavano’s 3.00 ERA that year was compiled under the best possible circumstances. He was in a league without a designated hitter, in a pitcher’s park, and in front of a good inner defense. Pavano showed excellent control, but his weak strikeout rates were sure to translate poorly to the American League, the DH, and the questionable defense of the Yankees’ middle infielders, if he could even stay healthy long enough to pitch.

When the Yankees signed Giambi after the 2001 season, they were in desperate need of a first baseman or a designated hitter. An aging Tino Martinez was only superficially productive given the number of good hitters who were playing at first base. David Justice, the primary DH, had reached the end of the line. Giambi (a .308/.412/.545 hitter up until that point in his career) seemed to be one of the game’s elite batsmen.

So he was, and so, to a large degree, he has remained. There are few players in the game who possess a better combination of the two qualities that generate offense, the ability to reach base and sock the ball for distance. Although Giambi has lost the ability to hit for the kind of high averages that he did with the Oakland A’s, his on-base percentage has remained well over .400 as a Yankee. His slugging percentage has likewise remained robust, staying above .500 in more than 700 games in New York. Coming into this season, Giambi ranked seventh in on-base percentage among players with 2000 or more plate appearances since 2001, and 16th in slugging percentage.

Even in 2004, when Giambi’s season was destroyed by injuries and illness, he kept his on-base percentage high at .342 by drawing 47 walks in 80 games. Giambi’s patience has offered multiple benefits to the Yankees, not only giving them baserunners, but also eating into the pitch counts of opposing starters and speeding the entry of mediocre middle relievers, where the real damage can be done. Because of this, Giambi is arguably one of the few hitters in the game who is valuable even when he slumps. Although his batting average for May is an ice-cold .136, Giambi has drawn 13 walks for an OBP of .356; the league average for the month is .340.

None of this is to say that Giambi is an admirable figure. It is understandable that Giambi does not want to open himself to possible sanction by making a clean, public confession of his experiences with performance-enhancing drugs, but he trips over the subject with embarrassing regularity. His responses to accounts of his BALCO testimony, rumors of a tumor in his pituitary gland in 2004, or his allegedly having failed a test for amphetamines, have been typified by the general apology he offered for unspecified transgressions in 2005. Ironically, in an effort to avoid censure for cheating, Giambi’s waffling, mealy-mouthed avoidances were what convicted him in the court of public opinion. Full disclosure at least would have given fans the option of forgiveness. Instead, he has left the image of a ballplayer better at staying away from the truth than he is from the infield shift.

Still, pennant races are won not by good guys, but by good ball players. Carl Pavano was a joke. Giambi is a hitter. The demise of the former merely brings a pointless saga to its inevitable end. If Giambi is traded, his replacement might be easier to like, but he’ll almost certainly be easier for hitters to retire as well.

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