Sergachev was injured during the second period of Tampa Bay's 3-1 road loss to the New York Rangers on Wednesday night.
The 50 rookie skaters in these playoffs are the most since teams used 54 in 2005-06. That could be a reflection of teams having greater trust in young players arriving from junior hockey or college, or the need to stock rosters with cheap talent as a greater percentage of the salary cap is devoted to the elite.