
Check Spain last year at the 2009 Eurobasket (European Championships):
Group stages:
Serbia 66–57 Spain
Spain 84–76 Great Britain (GB had a crappy team, playing without Deng & co.)
Spain 90–84 Slovenia (with a lot of luck)
Turkey 63–60 Spain
Spain 84–70 Lithuania
Poland 68–90 Spain
They ended up finishing 4th in the group, the LAST spot advancing.
Then came the knockout stage:
Spain 86-66 France (Quarterfinals; France was 1st in the other group, never losing a game, ending the tourney 8-1, this was their single lost game, and they lost by 20!)
Spain 82-64 Greece (Semifinals)
Spain 85-63 (Final)
Basically cruising through the whole thing.
Or think about the 2008 Olympics. The Spanish team that played in group stages simply wasn't the same one that played in the Final.
They barely even won against China after OT, for christ's sake.

I'm not going into if that's the right strategy or not, it does seem to work for them ... But I don't think anyone can really argue they play anywhere near 100% in group stages.