15 best trades in St. Louis Cardinals history

#5 - Mark McGwire (1997)

Cardinals acquire: 1B Mark McGwire
Athletics acquire: RHP Eric Ludwick, RHP T.J. Mathews, and RHP Blake Stein

Total surplus fWAR: 22.1

The first name inside the Cardinals' top five best trades of all-time needs no introduction. But I'm going to give one anyway.

Mark McGwire spent 12 years mashing home runs with the Oakland Athletics to begin his career, winning the 1989 World Series under manager Tony La Russa, and was drafted by then-Athletics' farm director, Walt Jocketty.

McGwire was a superstar with the Athletics, with the best season of his tenure in Oakland coming in 1996 when the first baseman slugged 52 home runs and posted a 1.198 OPS and 196 OPS+ that season. With former manager La Russa in St. Louis now and Jocketty running the show under the new DeWitt ownership group, the stars were aligning for the Cardinals to make a swing for one of the best players in the game.

The Cardinals desperately needed a jolt of energy. They had not been to a World Series since 1987, and despite losing in seven games in the NLCS in 1996, they had six losing seasons in the 1990s up until that point. While the arrival of La Russa, Jocketty, and new ownership seemed to indicate brighter days to come, McGwire's arrival seemed to put the Cardinals back on the map.

With McGwire in a contract year and the Athletics in the midst of a losing season, they deal their first baseman to the Cardinals for three pitchers who wouldn't amount to much for them, and McGwire would go on to crush 24 home runs in just 51 games for St. Louis down the stretch, filling Busch Stadium and setting up one of the most exciting seasons of baseball in 1998.

Credited with "saving baseball" that year, McGwire and Cubs slugger Sammy Sosa got into the home run chase, where the pair, along with Ken Griffey Jr., chased the single-season home run record, which McGwire achieved with 70 home runs that season. Even after beating Sosa in the chase for 70, McGwire finished second to him in MVP voting, and the Cardinals would miss the playoffs.

McGwire only played four and a half seasons with St. Louis and still ranks sixth all-time in franchise history with 220 home runs and 17th in walks. McGwire's 1.111 OPS as a Cardinal would have ranked first all-time had he qualified for the leaderboard.

McGwire's stint in St. Louis may have been short, but it was extremely impactful and one of the most memorable stretches in baseball history. Financially, the excitement he brought to the ballpark helped launch the next decade of Cardinals baseball. The club hit three million in attendance once in franchise history prior to McGwire coming to St. Louis, and they averaged 3,216,774 fans at the ballpark over the four full seasons he played with the Cardinals. With Albert Pujols sliding into McGwire's shoes, that started a two-decade-long run of Busch Stadium being packed to the brim every single year.