Admittedly he didn't do well yesterday, he was quite shit even, I'm not denying that, but how is he going to get back to form if he never gets played? Precisely why he didn't start, since it was obvious he wouldn't be up to form. They're putting him back a little at a time. They didn't do any worse with him there either, they still would have been shit without him.
Also you can't deny that in normal circumstances, Torres and Villa are a powerhouse and they both need each other. When that connection is made, goals are aplenty. The midfield is greatly important too and it was also lacking, but Torres is quite an important link as well.