St. Louis was coming off a 91–71 (.562) season and first place in the National League Central, followed by a quick playoff exit when they were swept in the NLDS versus Los Angeles.

Pitching coach and long-time LaRussa partner Dave Duncan, who earlier in 2009 had expressed displeasure with the franchise after his son Chris was traded, also agreed to return.

[2] Mark DeRosa, acquired from the Indians via an in-season trade in 2009, left St. Louis via free agency, signing with the San Francisco Giants on Dec.

[3] Troy Glaus, who hit 27 home runs as the third baseman for the 2008 Cardinals but was limited to 29 at-bats at the end of 2009 due to a shoulder injury, signed a contract with the Atlanta Braves on Jan 5 after passing a physical.

[5] The same day, Khalil Greene, who started 2009 as the everyday shortstop for St. Louis but was sidelined with social anxiety disorder, signed a one-year deal to be a utility infielder for the Texas Rangers.

[8] The contract includes a full no-trade clause, an average $17.0M per year salary through 2016, and a $17M vesting option for 2017 which will occur if he makes the Top 10 in the 2016 MVP voting.

[17] Jaime García, a Cardinal draft pick who underwent Tommy John surgery in 2008 after a cup of coffee with the big-league club, won the fifth-starter role in spring training.

Concurrent with Lopez's trip to the DL, the Cardinals sent Allen Craig to Memphis, recalled infielder Tyler Greene, and called up for his big-league debut Jon Jay, their second pick in the 2006 draft.

St. Louis lost 3 of 4 on the road to the East-leading Phillies, then, after taking two of three from Pittsburgh, returned home and were swept in three games by the Houston Astros, who were the worst team in the league prior to the series.

Brad Penny hit a grand slam in the third inning that proved decisive in St. Louis's 9–5 victory over the Anaheim Angels on May 21, but suffered a strained lat muscle in his back, apparently on the swing, and left the game immediately.

[33] St. Louis lost a second starting pitcher five days after Penny, when Kyle Lohse went to the DL on May 27 (retroactive to May 23), after being diagnosed with exertional compartment syndrome in his right (pitching) arm.

[34] Shortly thereafter further roster moves resulted in the demotion of Joe Mather and Salas, and the promotion of two pitchers making their major league debuts: former Cardinals first-round draft pick Adam Ottavino and minor-league veteran Evan MacLane.

Further bench maneuvering took place on June 5, when the Cardinals signed veteran outfielder Randy Winn, recently designated for assignment by the Yankees.

[41] Adam Wainwright threw a complete game two-hitter on June 4, and the Cardinals beat the Brewers 8–0, retaking sole possession of first place.

Seeking to shore up a rotation with gaping holes in the back end after the loss of Penny and Lohse, St. Louis acquired pitcher Jeff Suppan, a veteran of the 2006 World Series champion Cardinals and the MVP of the 2006 NLCS.

[45] On June 30, Albert Pujols had his 37th career multihomer game at Busch Stadium tying Stan Musial's franchise record by a Cardinals' player.

[47] The Cardinals, slowed by nagging injuries to Freese and Ludwick, plagued by poor performances from the back end of their rotation, and further weighed down by the season-long slumps of Ryan, Schumaker and Molina, trod water in June, going 13–13 to finish the month at 43–35.

On July 3, Ryan Ludwick went on the DL after he aggravated a prior left calf strain while exercising on a treadmill, and outfielder Jon Jay was recalled to take his place.

[49] Yadier Molina was voted starting catcher for the NL squad despite having one of the worst seasons of his career, with a .229 batting average on the day the rosters were announced.

Leading 9–3 going into the bottom of the ninth, Dennys Reyes and Ryan Franklin combined to give up nine runs to the Rockies, with Seth Smith's three-run walk-off homer capping an amazing 12–9 Colorado victory.

[52] After the Rockies completed a three-game sweep the next day, the Cardinals traveled to Houston and took two of three to go into the All-Star Break with a 47–41 record, one game behind the first-place Cincinnati Reds.

[60] Jason LaRue suffered a severe concussion after being kicked in the face by Reds pitcher Johnny Cueto, leading the Cardinals to call up minor-league catcher Steven Hill for his big-league debut.

[61] The Cardinals swept the Reds in three games, dealing Cincinnati its first series loss since the All-Star Break[61] and retaking sole possession of first place in the NL Central.

[67] After Freese's season-ending injury and a horrific slump by substitute 3b Felipe López, who was batting .165 since July 22,[68] the Cardinals acquired Pedro Feliz from the Houston Astros on Aug. 19.

The Cardinals slipped to a ghastly 5–12 after the sweep of Cincinnati for the remainder of the month, with 11 of those losses coming to teams with losing records (the Cubs, Brewers, Pirates, Nationals, and Astros).

Missouri native and longtime Chicago White Sox announcer John Rooney joined Shannon in the broadcast booth in the inaugural season with the new station.

On September 11, Albert Pujols reached 100 RBIs for the 10th consecutive year and drove in all three runs giving him 102 for the season, but the team lost in extra innings 6–3 at Atlanta.

[76] On September 19, catcher Jason LaRue, still suffering from the severe concussion he received on August 10 when Cueto kicked him in the head numerous times, announced his retirement from baseball effective at the end of the season.

[79] Pitcher Jaime García joined Molina on the shelf when the Cardinals decided he would sit out the remainder of the season, citing his Tommy John arm surgery (in September 2008) and heavy 2010 workload.

Garcia led all rookie pitchers with 13 wins, and posted the fourth-best (2.70) ERA in the NL,[80] One bit of good news penetrated the Cardinals' terrible month: Adam Wainwright won his 20th game on September 24.