The pair both played in the reserves on Tuesday, Fredi after a two month lay off with a groin problem and Don after a nine month spell on the sidelines with a cruciate injury.
Says Glenn: "Fredi will definitely start and Don will probably be a substitute as Steve Lomas is still injured.
"It is good to have them back and they are very positive about going into battle."
Paul Goddard is equally delighted and adds: "We have sorely missed Fredi because he gives another aspect to our game.
"Jermain and Paolo will be the first to admit you need that little bit more height up front at times, and, even though Fred sometimes doesn't jump his full height, he is 6'4" so he is a fair way up there to start with.
"He does give us a different dimension and he is fantastically skilful with his feet at times, so he is vital.
"He has been working very hard with the fitness people and had a full week of football as well as 60 minutes in the reserves.
"It is a pity we are not playing sooner than Monday night rather but we just have to get on with it. I'll be at a game scouting at the weekend."
It is impossible to say how long Fredi will play for but Paul says: "A lot will depend on how the game goes. We will be dictated to by Fredi, but one thing is for sure, we don't want him to break down again and if he feels too tired we will have to take him off."
As for Don, Paul says: "Don has had two reserve games back since his little set back after he had played in two games - but he has had a major injury.
"He is desperate to play again, and we are desperate to have him back, but it must be at the right time. It is something the manager will be talking to Don about."