Erik Karlsson proved to be an Achilles heel for the Washington Capitals Thursday night. And, he helped pave the way to the post-season for the Senators. After suffering a 70% cut to his Achilles tendon only 10 weeks ago, the Senators' top defenceman made a heroic return as the club qualified for the playoffs with a 2-1 OT victory over the Caps at the Verizon Center. Sergei Gonchar scored the winner with 4:13 left in OT by putting a blast by Washington's Michal Neuvirth on the power play to put the Senators into the playoffs. Jakob Silfverberg also scored for Ottawa, while Karlsson had two assists. "We came here with a goal -- two points -- and we got them," said Karlsson, who played 27:11 and had eight shots on net. "I didn't feel quite as comfortable as I used to. Overall, it was a solid game. There were some mistakes. Only Alex Ovechkin was able to beat Craig Anderson. It was only the second time since 2006 -- and the first time in three years -- the Senators have won a game in Washington. Ottawa knew what was on the line and didn't want to have to worry about trying to get points on the weekend. "A lot of guys counted us out of it. We had a lot of injuries in the beginning and I don't think anybody was believing that we were going to make it. It's a great feeling because it proves those guys who didn't believe in us wrong," said Gonchar. "It was a good feeling. We haven't been scoring as many goals and to score a game winner to make the playoffs is huge. We're happy. I'm not just happy I scored a goal, I'm happy we're going to make it to the playoffs."