The incident occurred in the first period of Boston's 3-2 home win over Pittsburgh on Saturday. After Marchand was tripped after trying to make a pass out of Boston's zone, Neal hits Marchand's head with his knee as he skates by.
Neal received a minor penalty for kneeing on the play.
NHL director of player safety Brendan Shanahan said in explaining the suspension that Neal had a clear view of Marchand on the ice and did not attempt to get out of his way.
The suspension will cost Neal US$128,205.15.