Viduka remained on Tyneside when his Newcastle United team-mates took on Arsenal in an FA Cup fourth round tie on Saturday.
Viduka To Face Arsenal!
But he has now fully shaken off the calf injury he suffered on the eve of the Bolton Wanderers game the previous weekend, and Keegan believes his return will give his side a lift after their 3-0 cup loss.
Keegan: "Mark Viduka will definitely be back for us tomorrow night.
"Because he had been out for a week, I just said to him to stay at home and get himself a little bit sharper over the weekend.
"I was always intending to play Mark on Tuesday night, because I want to have a look at different combinations, and that's not me rotating, it's me honestly trying to look and search for little things that we can build on.
"We sort of guessed Arsenal would play their strongest team against us on Saturday because of what happened to them at Spurs in midweek.
"They couldn't really take a chance with us, but I wouldn't be surprised if Arsene Wenger takes a chance with us on Tuesday night when he sees the video of Saturday's game.
"He'll probably think he can cause us some problems with some of his fringe players he has got."