Blackwell commented: "We are missing Darius because I wanted him to stay fit to allow me to bring Beatts back slowly, giving him 45 minutes in the reserves here and 20 minutes with the first team there.
"James is having to play even though he hasn't yet regained his touch properly and I don't want him losing confidence because of that."
Sun Jihai is still suspended due to his dismissal against Coventry City. It's not looking too good on the Hornets' side of things. International goalkeeper Mart Poom will be sidelined due to a dislocated shoulder. Favoured centre-back Jay Demerit is also a doubt ahead of the trip to Bramall Lane.