(Updated Dec. 18, 2018)
Seeking a starter to replace Woody Williams in the rotation, the Cardinals used a prospect, Dan Haren, to help land an ace, Mark Mulder.
On Dec. 18, 2004, the Cardinals acquired Mulder from the Athletics for Haren, reliever Kiko Calero and first baseman Daric Barton.
The Cardinals were praised for adding Mulder to a rotation of Chris Carpenter, Jason Marquis, Jeff Suppan and Matt Morris.
Haren, though, turned out to be more durable than Mulder.
Mulder had one strong season for the Cardinals, suffered shoulder ailments and pitched his final game for them in 2008 at age 31.
Haren was 6-10 in two seasons (2003-2004) for St. Louis, but developed into one of the most consistent pitchers in the majors. Haren had 11 seasons in a row of double-digit wins and made 30 starts or more in each of those years.
Haren, whose last season was 2015, posted a career record of 153-131. He was 147-121 after leaving St. Louis. The right-hander pitched for eight teams: Cardinals, Athletics, Diamondbacks, Angels, Nationals, Dodgers, Marlins and Cubs.
After compiling an 81-42 record in five years with the Athletics, Mulder was 16-8 in 32 starts for the 2005 Cardinals. The left-hander went a combined 6-10 for the Cardinals from 2006 to 2008.
Making a splash
After they were swept by the Red Sox in the 2004 World Series, the Cardinals had four prominent players depart as free agents _ Woody Williams (11-8 in 2004), shortstop Edgar Renteria, catcher Mike Matheny and second baseman Tony Womack.
Eager to make a splashy move to show the Cardinals would fight to repeat as National League champions, general manager Walt Jocketty spoke with his Athletics counterpart, Billy Beane, about Mulder and starting pitcher Tim Hudson.
On Dec. 16, 2004, the Athletics dealt Hudson to the Braves for pitchers Juan Cruz and Dan Meyer and outfielder Charles Thomas. Two days later, the Cardinals got Mulder.
Elite starter
“This is something we’ve been working on for two or three weeks,” Jocketty said to the St. Louis Post-Dispatch. “We’ve been going back and forth between Hudson and Mulder and we felt like, in our case, we had control of Mulder for an extra year (on his contract) … Both are quality, top of the rotation starters.”
Post-Dispatch columnist Bernie Miklasz described Mulder as “an elite starting pitcher” and “a legitimate front-of-rotation starter.”
From 2001-2004, only Curt Schilling had more wins (74) than Mulder (72).
“He’s an intelligent guy, a great athlete, a great fit,” Jocketty said of Mulder.
Red flag
Miklasz and his colleague, reporter Derrick Goold, did note, however, Mulder had faltered in the second half of the 2004 season after starting the All-Star Game for the American League. Mulder was winless in his last seven 2004 starts, posting an 0-4 record and 7.27 ERA. Overall, Mulder was 17-8 in 2004 but with a 4.43 ERA.
Wrote Miklasz: “Is he wearing down after averaging 212 innings over the past four seasons?”
Mulder denied he was weakened or injured.
“We took our time and thoroughly researched this … As far as we’re concerned, he’s fine,” Jocketty said. “There are no physical problems at all. We made sure.”
Said Mulder: “I wasn’t hurt at all … There was nothing wrong with me.”
Asked to explain why Mulder was ineffective in the second half of 2004, Jocketty replied, “He put a lot of pressure on himself … He tried to do too much.”
Swift start
Any concerns about Mulder were erased early in the 2005 season. He won seven of his first nine decisions for the Cardinals. After stumbling in June (2-3, 7.18 ERA), Mulder recovered and was a combined 7-3 over the last three months of the season. He was especially effective against left-handed batters, limiting them to a .191 average in 2005.
Haren, meanwhile, had 14 wins for the 2005 Athletics, posting a 3.73 ERA in 34 starts. Calero contributed four wins and a save in 58 relief appearances.
In 2006, Mulder won five of his first six decisions for St. Louis before the shoulder woes began. Mulder made two starts after June 20 and finished the 2006 season at 6-7 with a 7.14 ERA. He was 0-3 with a 12.27 ERA for the 2007 Cardinals; 0-0 with a 10.80 for the 2008 Cardinals.
RetroSimba 
When they made the Mulder/Haren trade with the A’s, Daric Barton was the guy the Cardinals hated to give up and everybody thought was going to be a star. He never really amounted to much.
Good points, thanks. Daric Barton was the Cardinals’ first-round draft pick in 2003 and batted .313 for Peoria in 2004. In 8 major-league seasons, all with the Athletics, he hit .247. His best big-league season was 2010 when he produced 152 hits and drew 110 walks and had an on-base percentage of .393.