By Thomas Neumann Tampa Bay locked up the 24-year-old defenseman amid a flurry of moves. View the original article to see embedded media. The Lightning made long-term commitments to three players Wednesday, including an eight-year, $68 million contract extension for defenseman Mikhail Sergachev. The pact, with an annual average payout of $8.5 million, places Sergachev among the top-earning defensemen in the NHL. The 24-year-old Sergachev recorded seven goals and 31 assists in 78 games last season. The No. 9 pick in the first round of the 2016 NHL draft by the Canadiens, he boasts career totals…