I haven't seen anyone post the final numbers yet for the season, so here goes:
Before signing the extension this year:
37 games, 21 goals, 33 assists, 54 points, +5, (20:16 ice time per game)
(47 goals, 73 assists, 120 points, +11) over an 82 game pace
Since signing the extension:
45 games, 19 goals, 25 assists, 44 points, -4 (19:38 ice time per game)
(34 goal, 46 assist, 80 points, -7) over an 82 game pace
Just the raw numbers. Maybe it has to do with how productive his linemates were, maybe other factors were involved. But from the day he signed the extension, his pure production is down significantly.
FYI over the same time period, Marner and Matthews production was up since that date, Tavares points were down but his goal production went up.