The team said Staal would probably not play for five to six weeks, Sports Network reported Thursday.
The Penguins are set to open the regular season Oct. 7 against Philadelphia.
Staal suffered a lacerated tendon in his foot during Game 1 of the Eastern Conference semifinals against Montreal. He underwent surgery and returned for Game 4 of the series, but developed an infection during the off-season,
"Jordan developed a post-op infection in his foot, and it can require several procedures to ensure that all infected tissues are removed," Penguins team physician Dr. Charles Burke said.
Staal has played in all but one game in his four-year stint with Pittsburgh and last season scored 21 goals with 28 assists for 49 points.
"While we know he is disappointed that he will miss the start of the season," Penguins general manager Ray Shero said, "he will now be able to make a full recovery and get back on the ice early in the season."