Kelly accompanied the Bruins on their flight from Ottawa to Pittsburgh, but Boston coach Claude Julien said the team was not able to fully evaluate the extent of Kelly's injury Tuesday, as had been planned.
"There's some swelling, obviously, so it's hard to say where he's at right now," Julien said about an hour before faceoff of the Bruins' game against the Penguins. "We'll probably be able to give an update in the next day or so once he gets home and the swelling goes down so it will probably be a little clearer then.
"We're anticipating and hoping for minor, but for me to predict right now would be careless."
Kelly was injured while absorbing a hit from Senators forward Chris Neil early in the second period of what was a 3-2 shootout win for the Bruins on Monday.
Veteran winger Jay Pandolfo will take Kelly's place in the lineup Tuesday, playing on the left side of the Bruins' third line. Rich Peverley moves into Kelly's spot as the unit's center, with Jordan Caron moving from left wing to right wing.
"That's the beauty of having guys who play all those positions," Julien said. "We've always felt fortunate to have all those centers for that reason -- and here's an opportunity to take advantage of it."
Kelly, who has two goals and four assists in 23 games this season, has won 60.9 percent of his faceoffs. Peverley is not far behind, though, at 59.9 percent.
An eight-year National Hockey League veteran, Kelly's next goal will be the 100th of his career.