Trading A.J. Pierzynski made sense. Joe Mauer was thriving in the upper minors, so the Twins had a cheap, young catcher ready to contribute. They had even less payroll flexibility than they do now, and Pierzynski was about to become expensive.
Twins GM Terry Ryan obtained prospects Boof Bonser and Francisco Liriano for Pierzynski, but as Ryan told the Minneapolis Star Tribune at the time, Joe Nathan was the centerpiece of the trade.
"We feel good about Nathan coming back," Ryan said. "He's a major league guy who has been tested and who is talented."
The Giants called on Nathan 78 times in 2003 and he responded with a big year. The righty struck out 83 batters in 79 innings, allowing just 51 hits and 33 walks for a 2.96 ERA. Nathan's tenure with the club ended badly, however. He allowed three runs to the Marlins in the NLDS before storming off the mound.
Some thought Nathan had closer potential, but Sabean wasn't convinced.
"Whether someone is going to be a closer or a front-line starter is a lot of speculation," Sabean told the San Francisco Chronicle. "That is not necessarily the organization's view of the world."
The Giants had Yorvit Torrealba around, but they admired Pierzynski's play so much they couldn't pass up the chance to make a trade.
"It's not often you can send a reliever and two prospects away for a front-line, All-Star, left-handed hitting catcher," Sabean said.
That left-handed hitting catcher interested a variety of clubs. The Cubs, Padres and Orioles were among the teams who saw lots to like in the backstop. At 26, Pierzynski had a lifetime average of .301 and a career OPS of .788. He had just established career highs in every offensive category of consequence and was under team control for three more seasons.
Pierzynski hit .272/.319/.410 with 41 extra base hits for the Giants in 2004, but he didn't fit in with his new club. An anonymous teammate called him a "cancer" and a number of Giants told the Oakland Tribune that they wouldn't mind seeing him traded. Pierzynski remained on the team for the rest of the season, but his tenure by the Bay ended months later when the Giants non-tendered him.
In 2006, when Liriano seemed capable of replacing Johan Santana atop the Twins' rotation and Bonser looked like a solid starter, too, this trade seemed even more lopsided that it does today. Liriano had just struck out 144 batters in 121 innings en route to a 2.16 ERA. Bonser, a 2000 first rounder, had just pitched 100 innings of 4.22 ERA ball.
But Liriano underwent Tommy John surgery in 2006 and he hasn't matched his initial success since. Bonser's performance fell off in 2007, he was bumped from the rotation in 2008 and he missed 2009 because of shoulder surgery.
Meanwhile, Nathan has improved in Minnesota. He has never had an ERA above 2.70 or saved fewer than 36 games with the Twins. He's made three All-Star appearances since Sabean sent him to the AL and has kept his WHIP below 1.00 in five of his six seasons in the Junior Circuit.
At the time of the trade, Bruce Jenkins of the San Francisco Chronicle wrote that "Giants fans won't miss Joe Nathan," calling the deal a "steal" for Sabean. Nothing seems further from the truth now, but the deal didn't appear lopsided in 2003. The Giants gave up a reliever with a history of shoulder problems and two unproven, but promising prospects for an affordable catcher who should have been entering his prime.
Still, the deal is a blemish on Sabean's record and a major reason the Twins have won three division titles since.