The Sox had listed Franklin Morales as Wednesday's starter for the final game of the road trip, but have re-arranged their rotation.
Aaron Cook, who tossed an 81-pitch complete game shutout Friday, will pitch Wednesday afternoon.
For the four-game set with the Yankees at Fenway beginning Friday, the Sox will start Josh Beckett in the series opener, lefties Morales and Felix Doubront in the day-night doubleheader Saturday, with Jon Lester pitching the finale Sunday night.
Morales, meanwhile, will be starting on eight days rest and will be available out of the bullpen Tuesday night and Wednesday afternoon.
"We're trying to make the best use of what we have,'' Valentine said.