He was struck in the mask on a shot by new teammate Brian Rolston during practice Wednesday and underwent tests Thursday, the team said Friday.
DiPietro didn't play in any of New York's first three regular-season games and has played a total of 39 games the past three seasons. The 30-year-old goalie is in the sixth season of a landmark 15-year contract with the Islanders.
DiPietro, the backup to goalie Al Montoya in the first two games, was scratched Thursday night. Montoya started again Thursday in the Islanders' 5-1 victory over the Tampa Bay Lightning, with Evgeni Nabokov as the backup for the first time since he joined the Islanders.
DiPietro missed most of the 2008-09 and 2009-10 seasons because of a knee injury. He also had surgery on both hips since the Islanders drafted him No. 1 overall in 2000.
Last season, DiPietro was sidelined for several weeks because of broken bones in his face caused by a punch from Pittsburgh goalie Brent Johnson on Feb. 2. DiPietro was felled by a left hook above his right eye, and the broken bones and swelling in his knee kept him out until March 19. He played in five games after returning.
DiPietro played in a total of 13 games in the two previous seasons because of his troublesome knee. He has never played more than 63 games in a season.
His concussion troubles began in March 2007 when he crashed into Montreal forward Steve Begin as he charged to get to a puck at the blue line. DiPietro made a brief return for a few games, but was sidelined again by another concussion that put him out for the rest of the regular season. He did get into some playoff games that spring.
In other news Friday, the Islanders said center Jeremy Colliton has cleared waivers and been assigned to Bridgeport of the American Hockey League.