Morton ruptured the flexor tendon in his left-ring finger during training at AAMI Park on Wednesday.
He is likely to have surgery this week to repair the tendon.
Melbourne Coach Dean Bailey said it was disappointing to lose a player of Cale’s calibre on the eve of the NAB Cup.
“Cale is a very positive person and while this is a setback, he will do everything possible to keep his fitness at an elite level to give himself the best chance to push for senior selection as soon as possible,” he said.
Morton has played 50 matches in three seasons, but was limited to 10 last year after missing the opening eight rounds through injury.
He remains one of Melbourne’s most important players long-term.
Morton was selected at No.4 in the 2007 NAB AFL Draft.
