Defenseman Justin Schultz left the game 4:32 later following a collision with Mike Hoffman that sent him sliding into the end boards.
Penguins coach Mike Sullivan did not provide updates on Hornqvist, Rust or Schultz following the game.
Suddenly, with 10:52 remaining in the first period, the Penguins were without their first-line right wing (Rust), their net-front presence on the top power-play unit (Hornqvist) and the quarterback of that unit (Schultz).
Pittsburgh was vulnerable. It responded by controlling the final two periods by outshooting Ottawa 21-13.
"Our defensemen were unbelievable," center Sidney Crosby said. "They were at five for a long period of time. That's not easy. So, I think that they hung in there, made a lot of great plays and allowed us to have possession of the puck and create things offensively."
Not that it surprised Crosby.
"We try to have high expectations," he said. "Whoever's in whatever role or whatever guys need to do out there, I think they're willing to do it."
At one point, the Penguins kept the Senators from having a shot on goal for 18:53. After Chris Wideman's snap shot with 3:47 remaining in the second period, Ottawa didn't have another shot until Zack Smith backhanded one on goalie Marc-Andre Fleury with 4:54 left in the third.
When asked what he did during that span, Fleury jokingly responded, "Wait."