Exactly!!!

I can understand having to bring in a substitute partner at the last minute who needs to do the choreography that was ALREADY learned and trying to fit that new partner in as seamlessly as possible. But, Derek got hurt like on Tues, at the
beginning of the next dance week. That was plenty of time to transition Sasha in. MUCH of the new dance choreography was based around Derek SITTING, so he could be folded into the dance. So that was NOT
existing choreography. SASHA should have been the one to choreograph HIS number this week and any weeks going forward if HE is the one dancing with Nastia.
Derek needs to decide by NEXT Monday whether he is going to be Nastia's partner or not. It's not fair to the other dance teams that she gets interchangeable dance partners. I highly doubt that if Val got hurt and Maks or Tony stepped in, that in 3-4 weeks time, Val would be allowed to come back and Maks or Tony are out again. ANY other dance pro would be forced to choose whether they could come back in about a week's time frame or give up the pro spot to another
permanent dancer.
I do believe that Tony did step in, years ago and take over for another pro dancer. I forget who the star was.
Derek needs to suck it up and decide. He wasn't originally going to be in the show this season. So, he shouldn't have a problem stepping down, since he wouldn't have won the mirror ball anyway, not being on the show. Sasha should be dancing with Nastia ans a poor substitute, they survive the next few weeks and Derek sweeps in the last couple weeks to win the mirror ball with her.
And IF Derek is able to get a walking/dancing cast put on his foot, what does that do for Noah? We already have ONE handicapped dancer, dancing with a missing side of his body. He's here to be an inspiration of what is possible with the human spirit and show a physical handicap is no reason to be sitting on the sidelines of life. He
obviously gets the sympathy/inspiration votes, (not to mention the patriotic votes.)
Then along comes Derek, also with a "handicapped" leg now, dancing in a cast, and you just know the judges are going to be cooing over what he's capable of doing in a cast - AND giving him sympathy/fudge factor votes for choreography around HIS disability. That makes Noah, who doesn't get to go home and take off a temporary cast in 4-6 weeks look like his sacrifice for our country is friggin chopped liver.

PLUS Noah will probably be going home soon, meanwhile Golden Boy Derek with his gimpy leg will make it to the finals.
ABC should just rename the show now:
Dancing With The Stars WITH Derek Hough because if at all possible, they aren't doing this show without him.