In Wimbledon, the top players would rather face Nadal in the first week of Wimbledon than championships match.
Nadal is most vulnerable in the first week as the grass is still green, which by the end of the second week will have turned into mud.
Most of the time, Rafa ups his game to meet the demands even in early rounds. Remember the 5 setter against Isner at RG . It happened in week 1 of the tournament . If your "Week 1 Rafa is weak " theory is true, how will you explain all the Masters' Title Rafa has. All of them are ONE WEEK tournaments .