There are a few factors in play. I think the two biggest are the quick transition from clay to grass, and the lack of wear on the 'show' courts. Players slide on the clay, and you can't do that for very long on grass without hurting a knee or an ankle. It takes different types of movement to play well on grass, and having only 2 weeks between the French and Wimbledon isn't very long for players to adjust to the change. That will improve in 2015, when they'll get a third week between those 2 majors.
The other factor is that Wimbledon doesn't let players practice on the featured courts in the days before the tournament. They want Centre Court and the other main TV courts to look pristine at the start of play. They look great on TV, but the grass hasn't been worn away by players running around on it.
This year's weather could also be part of it, as well as less players serving-and-volleying. That's been the case for several years, but the injuries that are occurring are when the players are either running wide behind the baseline or making a change of direction on the baseline.
It should get better after the courts get some more wear on them. Plus, the players still left after this week will have at least 3 matches behind them, and will be better adjusted to running around on the grass.
Nadal...straight sets
