The Ottawa Senators announced on Wednesday that their captain Erik Karlsson underwent surgery to repair torn tendons in his left foot, an injury that he suffered in the playoff run, which ended in the Conference Finals. In the team's announcement, they expect their leading defenseman to be back in action in around four months, which puts him in the middle of October, just a couple of weeks into the new NHL season, at the latest. Knowing Karlsson, he has been known to be a fast healer, so to have him ready on opening night wouldn't be a surprise.
It will be worth noting, however, whether or not he does miss any time, because there will be some points missed out on, if he is on the shelf to start the season. This past season, Karlsson registered 71 points in 77 games in the regular season, which ranked him as the 3rd best defenseman in scoring.