When a 27-year-old lefty with a history of durability hits the trade market, teams are going to show interest. Mark Mulder had an 81-42 career record and was still two years away from free agency when A's GM Billy Beane made him available five winters ago.
After losing the World Series, Cardinals GM Walt Jocketty decided to pursue the Oakland lefty. In late December of 2004, Jocketty acquired Mulder for three prospects: Kiko Calero, Daric Barton and Dan Haren. Jocketty told ESPN that he'd acquired a "top of the rotation-type pitcher" and he appeared to have done just that.
In spite of Mulder's youth, durability and reputation for winning, there were warning signs. As Goldstein pointed out, the A's wondered about Mulder's health when he struggled down the stretch in 2004. And in spite of his lofty win totals, Mulder started walking more batters, allowing more homers and striking out fewer hitters per nine innings in his final season as a member of Oakland's "Big Three."
Haren, who was 24 at the time of the trade, dominated the minor leagues. He had a 3.15 ERA in the minors, striking out nearly a batter per inning and walking very few hitters (1.6BB/9).
We know what happened from here. After a solid 2005 season, Mulder's shoulder and rotator cuff sidelined him and he hasn't been productive since. The Cards got the rights to one decent year and one poor one, but the deal stands out because they gave up so much.
Calero had a couple productive seasons for the A's and the 24-year-old Barton showed some promise in limited time this season. Haren, the centerpiece of the deal, excelled for the A's during his three-year Bay Area stay. He logged over 200 innings each season and netted the A's Brett Anderson, Carlos Gonzalez, Chris Carter, and others when they traded him to the D'Backs.
A huge win for the A's, but it's easy to see how the Cards were tempted by Mulder and why they were determined to bolster their rotation at all costs.