"Best-case scenario is six weeks. The realistic one is a few months," agent Paul Cohen told The Associated Press on Thursday. "We're hoping it's a couple months, but we won't know until they do further medical tests."
Cohen said team doctors will have a better feel for a timeline next week after "massive swelling and bleeding" subside. "It's a non-surgical tear, which could be a good thing."
Tulowitzki, the runner-up for NL Rookie of the Year last season, was injured while charging a grounder in the first inning at San Francisco on Tuesday night. He underwent an MRI exam on Wednesday, which found a complete tear of the tendon near his hip, team athletic trainer Keith Dugger said.
The injury is rare in baseball but is not uncommon in soccer players.
"He's just so disappointed for his teammates and the fans," Cohen said. "He just can't believe it, really. It's still sinking in."
Fighting through a season-long slump, Tulowitzki wasn't scheduled to play Tuesday night but was a late addition after second baseman Jeff Baker broke a blood vessel in the middle finger of his right hand during batting practice.
Following his sensational rookie season, Tulowitzki signed a $31 million, six-year deal, the largest contract ever signed by a non-Japanese or Cuban player with fewer than two years' of major league service.
The Rockies' first NL pennant was fueled by the 23-year-old star's phenomenal performance in the field, at the plate and in the clubhouse. Tulowitzki became a respected leader among established veterans including Todd Helton and Matt Holliday despite having played barely a year in the minor leagues.
He led big league shortstops in fielding percentage, got to many more balls than anyone at his position and even turned an unassisted triple play, just the 13th in major league history. He also set an NL rookie record for home runs by a shortstop (24) and batted .291 with 99 RBIs as the Rockies surged to their first World Series.
The crowds at Coors Field began a rhythmic chant for Tulowitzki, and Colorado set a big league record for fielding percentage.
His October exposure, however, created a thick book on Tulowitzki, and he had a hard time in April adjusting to pitchers armed with new scouting reports who busted him high and inside with fastballs before getting him to chase pitches down and away.
He was hitting just .152 with one homer and 11 RBIs in 105 at-bats when he got hurt.
Clint Barmes, the Rockies' starting shortstop in 2005 and '06, will fill in until Tulowitzki's return.