Mantha was assessed a five-minute major for boarding Senators defenceman Nikolas Matinpalo with just under 10 minutes remaining in the first period.
The Senators later announced that Matinpalo was ruled out for the remainder of the game with an upper body injury.
“It’s pretty obvious what the injury is,” head coach Travis Green said after the 4-1 win. “We’ll wait to see how he feels tomorrow.”
The hit came on a play at the New Jersey blue line, as Mantha chased Matinpalo and a loose puck towards the boards before pushing the defenceman from behind and down to the ice.
Players on both teams came together in a scrum as Matinpalo stayed down after the hit.
After getting to his feet and leaving the ice, Matinpalo went straight down the tunnel.
The Devils ended up killing off the five-minute penalty.
Mantha is in his first campaign with New Jersey after signing a two-year deal with the Devils in the off-season.
The 32-year-old had yet to find the scoresheet in New Jersey’s first four games of the season, averaging 13:40 of ice time per night.
The Senators return home to host the St. Louis Blues on Tuesday.