This is not good for Fed's rhythm at all but I also hate this too because I am worried about Mardy. Roger still has a tougher draw than Nole. With Isner losing and Murray and Berdych being on the other side I don't think Nole has anyone dangerous on his side except possibly Del Potro.
In this case, probably only helps Fed be fresher now that we are getting to the business end of the tournament. He's had plenty of play this summer so he's match ready. But agreed, hope it's not something serious with Marty and more just he wore himself out the other day.