The 23-year-old Duff announced the pregnancy on her official website over the weekend, with the news coming just as the couple celebrated their first anniversary.
"I can't believe it has already been a year, time really flies when you're having fun!" wrote the former "Lizzie McGuire" star.
"We also want to share the exciting news that…… BABY MAKES THREE!!! We are extremely happy and ready to start this new chapter of our lives."
The 30-year-old had one goal and five assists in his shortened campaign, and the forward has 365 points in 589 career NHL games.