The 35-year-old blue liner appeared in 61 games with the Boston Bruins last season and chipped in just one goal and 12 points while averaging 19:23 per game.
Seidenberg was once a solid, and underrated, defenseman but those days have passed. He brings nothing to the table offensively and his defensive game is deteriorating fast.
Over the last two seasons the Bruins have controlled 47.8% of the shot attempts and 47.3% of the goals at 5 v 5 with Seidenberg on the ice. Without Seidenberg the Bruins' numbers were significantly better as they controlled 50.9% of the shot attempts and 52.2% of the goals.
If he's willing to accept a tryout it can't hurt to bring him in with no strings attached but I think the Flames would be better off looking elsewhere.