Senators General Manager Bryan Murray confirmed that Kovalev -- considered a key to Ottawa's post-season hopes -- had completely torn the anterior cruciate ligament in his left knee and will require season-ending surgery, NHL.com reported.
"(Kovalev) has a completely torn ACL and a deep bone bruise, which has caused him a fair amount of pain," Murray told reporters. "He will have surgery in probably two weeks and certainly this year is over. The normal rehab, they tell me is, 3 1/2-to-four months.
"That's pretty much the playoff story for him at this point in time."
Kovalev suffered the injury Thursday during the Senators' loss at Tampa Bay and underwent an examination Friday.
The free-agent signee had racked up 49 points, including 18 goals, this season and was Ottawa's fourth-leading scorer, the Web site said.