Matt Grevers, the world No1 100m backstroke specialist who was said to have scratched from the 100m freestyle after semis last night, is back in: he will take up his place in that 100 free final tonight after all. 

In fact he was never officially out. USA Swimming announced after the semis that Grevers, third through to the final, had opted out. The governing body today said that it had made a mistake on the basis of "bad information".  

The swimmer's word may have been taken too literally: Grevers told the media in the mixed zone and is on camera after the semi as saying that he hoped he would be picked for the relay and was capable of a second drop on his time in a relay, adding: "As of now, I don't think I'll be doing the 100 free tomorrow to focus on the 200 back."

In fact, Grevers raced the heats of the 200m backstroke and then withdrew from that to focus on the 100m free.

Ryan Lochte has scratched, his decision throwing Jason Lezak (the 46.06 hero who had France crying on its croissants and Phelps still gunning for right golds in Beijing 2008) a lifeline. David Walters, next in line as an alternate, will not now make it.

In the face of Aussie Missiles and Rockets, the US 4x100m quartet could do with all the might it can muster.  

A paper exercise that may mean little come the moment but here's how the blades are sharpening up in 2012 as we head into the US final this evening:

Australia

• 47.10 Magnussen
• 47.63 Roberts
• 48.32 Targett
• 48.53 Sullivan

France

• 48.02 Agnel
• 48.38 Gilot
• 48.48 Leveaux
• 48.61 Bernard

USA

• 48.33 Adrian
• 48.48 Feigen
• 48.49 Phelps
• 48.71 Grevers