Splitter a below average defender? He's very probably the best defensive big man in Europe and will easily be an above average defender in the NBA - defence is Splitter's biggest strength. And a proficent scorer in the low post when there's little to no physical play? Even if that was true, there wouldn't be a problem, there's basically no physical play in the NBA relatively to the European game.
Why do you expect his numbers to fall? Have you also expected it for Manu, Scola, Marc Gasol, Ilyasova, Casspi, etc? Those numbers are excellent for a big in Europe, what kind of numbers do you think Scola was having?