United dropped to fourth in the Championship ahead of the latest international break following a goalless draw with city rivals Sheffield Wednesday.
Ahead of Saturday's short trip to Rotherham United for a lunchtime kick-off, there were fears that John Egan would be absent after picking up a calf injury on duty with the Republic of Ireland.
Egan, who was signed from Brentford in the summer for a fee that could rise to £4m, picked up the injury for Ireland in their game against Northern Ireland last Friday and was withdrawn from the squad to face Denmark on Monday.
But Wilder confirmed: "Everybody is okay and training today. We've got a full complement of players to choose from for the weekend's fixture.
"The medical staff for the national team made an assessment, John had a bit of a complaint during that game and they sent him straight back, which is the correct decision for all concerned.
"We're delighted they took the sensible approach and thankfully for us John is available for us at the weekend."
John Fleck was called into the Scotland squad while Kieron Freeman featured for Wales which was a major boost for the Blades.
"From my point of view it's great those boys have been recognised," said Wilder. "A lot of our supporters will definitely think it's long overdue regarding John Fleck.
"I'm very pro those boys getting international recognition. We had eight boys away on international duty and that's great for us."