Lehtera underwent surgery on Aug. 4. The Blues say he suffered the injury "at the end of last season."
According to the St. Louis Post Dispatch's Jeremy Rutherford, Lehtera suffered the ankle injury toward the end of the regular season. The team originally opted for rest over surgery, but the ankle still bothered Lehtera when he resumed skating.
Lehtera, 27, signed a two-year, $5.5 million deal with St. Louis in July 2014. He was drafted in the third round of the 2008 NHL draft.
Lehtera had 14 goals and 30 assists in 75 games for the Blues last season, his first in the NHL. He added two points in five playoff games.
- Rohan Nadkarni