The injury carried a minimum six-week recovery period, the source told ESPN, meaning Collier would not have been able to return this season had the top-seeded Lynx advanced beyond their best-of-five series against the Mercury.
The Mercury eliminated the shorthanded Lynx with their victory Sunday in Game 4 of the series.
Lynx coach Cheryl Reeve was ejected from Game 3 and earned a one-game suspension for her reaction to the play on which Collier was injured.