HOUSTON — St. Louis Cardinals outfielder Matt Holliday will have surgery Wednesday on his right thumb, an injury that could sideline him for the rest of the regular season.

Holliday was hit by a 94 mph fastball from the Chicago Cubs' Mike Montgomery last Thursday. Cardinals general manager John Mozeliak said Holliday could be sidelined through September.

"The procedure was the only chance to potentially get him back this year, so that's a big step to make," Cardinals manager Mike Matheny said Tuesday. "He wants to play."

The 36-year-old Holliday, a seven-time All-Star, is batting .242 this season with 19 home runs and 60 RBIs in 107 games. He would be eligible for free agency after the World Series if the Cardinals declined a $17 million option for next year and chose to pay a $1 million buyout.

Tommy Pham and Brandon Moss have seen time in left field in Holliday's absence.

Reliever Seth Maness was put on the 15-day disabled list and will have Tommy John surgery, which likely will sideline him until 2018. The Cardinals recalled right-hander Sam Tuivailala from Triple-A Memphis.

Maness was 2-2 with a 3.41 ERA in 29 relief appearances this year. He was on the disabled list May 13 to June 18 due to right elbow inflammation.

St. Louis has 12 players on the disabled list, including seven added since the start of August.