Coach D.J. Smith told reporters Friday that Talbot was "day-to-day" after taking a puck under his equipment in practice. The team announced Monday that the injury will keep him sidelined through the first month of the season.
Since 2013-14, Hellberg, 31, has appeared in four career NHL games with the Nashville Predators, New York Rangers and Detroit Red Wings. He spent the past five years playing primarily in Russia's Kontinental Hockey League.
Talbot's absence is a rough start to a hopeful season in Ottawa. The Senators made waves in the NHL offseason by trading for Chicago Blackhawks star Alex DeBrincat and signing former Philadelphia Flyers captain Claude Giroux, bringing them onto a roster of promising young players.