I feel Luongo had an excellent argument to be the best in the world if you have to pick someone from say 2004-2012 window and can sound underrated by moment.
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But, Osgood was good and quite experimented for the big moment and got the job done in the playoff for the RedWings for sure:
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.943 save percentage at even strenght in the playoff, .924 overall,....
Hasek was not bad in 2007, so it is not easy for the Wings to get an upgrade the only time it matter, the playoff and it is a bit costly, so I am not sure if the upgrade vs what they loose amount to much in 2007-2008-2009.
Maybe they are able to stay a contender longer after that with such a dominant goaltender too, that said goaltending was far to be an big issue for them in those playoffs.