I'm looking at the playoff scoring leaders during those years, particularly the mid to late 2000s were Thornton was in his prime. There's no denying his playoff numbers sucked but looking deeper I expected there might be some context to explain his lack of production. Well...
2005-06
After having the best season in franchise history, Thornton has 9 points in 11 games. He's tied with Cheechoo, but Marleau leads them in scoring with 15 points.
It's not like the rest of the roster lacked scoring, erhoff had 8, Preissing 7, Bernier 6, etc.
2006-07
Has the 2nd best season in franchise history (1st if you consider 2005 wasn't a full season with the sharks)
Leads his team with 11 points in 11 games in the postseason. The next highest leader on the shark? 4 other players tied for 6 points. I think it's fair to say he pulled his weight here relative to how the rest of his team did, even if "just" being a PPG is underwhelming in itself.
2007-08
Once again leads his team in scoring by a significant amount. He has 96 points when the next highest on the team (michalek) has 55. Not much to work with offensively.
Leads his team with 10 points in 13 games in the postseason. Underwhelming production once again, and his teammates aren't too far behind either. Pavelski and clowe are just a point below, Cheechoo and Marleau within 2 points, and there's no significant drop off within the rest of the roster.
2008-09
Leads his team in scoring once again, but this time has a lot more help offensively. Marleau isn't that far behind. Setoguchi and Pavelski have more points than last years 2nd best point producer.
Led his team with 5 points in 6 games in the postseason. Dan Boyle and Rob Blake, 2 defenseman, are a point behind him. The rest of the forwards are slacking with half a point per game or lower.
2009-10
Still led his team in scoring, but this time, Heatley and Marleau are a few points within tying Thornton for the lead while scoring far more goals. It's arguable whether Thornton was the best forward on the team at this point. At the same time though, this is the most help he's had offensively since 2005-06. Maybe with teammates on his level, he can finally not be the sole focus of opposing teams in the playoffs, allowing him to actually produce! Well..
With 15 games played, Thornton finishes.. 5th in scoring with 12 points! Pavelski leads the postseason with 17 points, being their only player above a PPG. But Boyle, Heatley and Marleau all outproduce Thornton.
So in this timespan, he led his team in playoff scoring 3 out of 5 times. Only 1 of those times he lead his team by a significant margin. Remember that this is the timeframe where he had 5 of his 6 top 10 point finishes in the regular season and led his team in scoring every year.
There's no way around it, those mid to late 2000s postseasons were shockingly underwhelming for a player of his calibre. His postseason totals from 2005 to 2009 were 47 points, 38 assists, 9 goals in 56 games. Marleau was just behind with 44 points, 26 goals in 55 games. The same Marleau that Thornton outproduced by 111 points during the regular season in the exact same timespan while playing less games.
Funnily enough, in 2010-11. After not being the scoring leader during the regular season for the first time as a Shark. He goes on to lead them in the postseason with 17 points in 18 games. There were a few teammates close to him, but this is Arguably a top 3 postseason of his career. Then he'd lead his team in points one final time the next year with 5 points in 5 games, and that was the end of him ever being the points leader in the postseason. I'll cut him some slack during the 2010s though since he was clearly no longer in his prime.
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