Jamal Mayers is a great guy. He has played in 915 NHL games over 16 seasons and has played in 63 postseason games. However he didn't play at all this postseason, which means he didn't play during the Finals, and that may cost him.
There are some very simple rules to getting your name engraved on Lord Stanley's Cup. You can play in at least one Stanley Cup Final game or play in half of your team's regular season games.