That's one way of looking at it. There's another one. These are the 8 semifinalists of the Madrid Masters in 2012:
Tipsarevic - Del Potro - Berdych - Federer
Radwanska - Hradecka - Azarenka - S. Williams
Not one of them made the finals of Roland Garros. Not one... Out of eight.
these players wouldn't have made the final even if they would've skipped madrid. most of them aren't that great on clay, only fed (and maybe silliams, but her bad rg-record is common knowledge) had a serious shot at the final at rg (azarenka still hasn't won a big clay-tournament). there's no great claycourter @wta since henin retired. and i doubt fed lost that semi against djoker 'cause he played madrid...