Martin was hurt Friday night in the closing minutes of the Timberwolves' 98-91 loss in New Orleans. X-rays taken Saturday morning revealed the fracture.
Martin is averaging 19.0 points, 3.3 rebounds, 2.0 assists and 32.3 minutes.
The Timberwolves already are without starting center Nikola Pekovic. He's sidelined by bursitis in his right ankle.