The Buffalo Sabres acquired Belliveau in a trade with the Pittsburgh Penguins on June 28, 2025. The full details of the trade are as follows: defensemen Conor Timmins and Isaac Belliveau to the Buffalo Sabres in exchange for a 2025 second-round pick, 39th overall (Peyton Kettles), and defenseman Connor Clifton.

The 2024-25 season marked Belliveau’s second professional season. He split it between the Pittsburgh Penguins’ minor league affiliates, the American Hockey League’s Wilkes-Barre/Scranton Penguins (22 games), and the ECHL’s Wheeling Nailers (25 games). Beliveau is an organizational depth defenseman who will likely struggle to earn a spot in the NHL; there is no fantasy value here, and therefore, no need to roster him in any league.

Belliveau spent the 2022-23 season in the QMJHL, where he played 55 games and recorded 46 points. In previous seasons, discussions about Belliveau’s tools consistently received high praise, ranging from his skating to his puck skills to his physical side of the game; however, this did not translate to the point production many would expect from a highly regarded prospect. This season, that all changed with Belliveau playing on the top pair for the Gatineau Olympiques for much of the season. Belliveau should be heading to Wilkes-Barre Scranton next year to play with the Penguins’ AHL team. This will be a big test to see if Belliveau can carry over the tools he refined in juniors to the pro game.

The Quebec-born defenseman showed a lot of improvement in his DY+2, but still failed to replicate the incredible offensive totals he posted in his DY-1. He was always going to be a project, a prospect due to his poor transition game and tendency to make mistakes. The Pens will likely be happy about the strides he took forward as an all-situations defenseman and leader this season. Still, another season of junior where he can dominate would boost his confidence and allow him to learn from his mistakes in a low-pressure environment. The Olympiques have a good young team with top prospects Zach Dean and Tristan Luneau, and Belliveau would be a candidate for captain. At 6-foot-2, 185 pounds, he possesses a pro frame and solid puck and distribution skills. If he can become an NHL defenseman, it should be viewed as a massive win for the Pens’ development team.