Neal, who has totaled 18 goals and 32 points in 39 games this season, joins team captain Sidney Crosby on the shelf after taking an accidental elbow from New York Rangers defenseman Michael Del Zotto in Friday's 2-1 shootout victory.
On the play, Del Zotto was blocking Neal from reaching the puck at the Rangers' goal line. His right elbow struck Neal fully in the face.
Pittsburgh had already lost Crosby, the NHL's leading scorer, to a broken jaw for an indefinite period.
The Pens, however, still lead the Eastern Conference with 58 points.