Staal will miss approximately 4-to-6 weeks with a knee injury suffered in Friday's game against New York when he collided with Rangers forward Mike Rupp.
The 23-year-old has totaled 15 goals and 21 points in 34 games this season.
Neal will be lost for "weeks" with a broken foot sustained when he blocked a shot in Saturday's contest against the New Jersey Devils.
In addition, Pens head coach Dan Bylsma said that forward Craig Adams, who was injured during practice on Sunday and aggravated a previously unknown injury, will be further evaluated on Monday.
Already without Crosby due to concussion-like symptoms, the Pens have struggled to keep pace in the Atlantic Division, falling to fourth with a 21-15-4 record following a 3-1 home loss to the Devils on Saturday.