Paul Dummett and Jack Colback have been ruled out of tomorrow's match through injury.
Colback had been due to fill in at left-back in place for Dummett, who suffered a hamstring injury against West Ham United last weekend.
But midfielder Colback is also unavailable because of a hamstring "niggle", according to head coach Steve McClaren, who has defensive quartet Fabricio Coloccini, Chancel Mbemba, Jamaal Lascelles and Daryl Janmaat available to play at Vicarage Road.
McClaren said: "Paul Dummett has a tight hamstring, but he should be back for the next game.
"Jack Colback's got a little niggle. We're not taking a risk."
McClaren also has defender Steven Taylor back from a long-term injury, though he is likely to be named on the bench.