The team was hit by the double blow last week, with both key players expected to be out for at least a month.
They join Jon Meades and Sean Rigg in the treatment room, while Danny Rose was only available for Saturday’s 2-2 draw with Cheltenham Town following a fitness test on the eve of the game.
An exceptional situation in the goalkeeping department saw the U’s sign Shwan Jalal on a one-month deal last Thursday, but there will be no other recruits.
The club set up a new development squad to bring through younger players this summer.
It saw five teenagers on the bench last weekend, and U’s boss Chris Wilder confirmed despite the new injury concerns there will be no activity in the loan market.
He said: “It is what it is, they are the bodies we have, there won’t be anybody coming into the club, so we will just use the players that are available for selection.
“That is where it’s at.”
It means Johnny Mullins will be partnered by Michael Raynes, the squad’s only other fit specialist centre back, during Wright’s absence.
The 25-year-old came in for his first appearance of the season on Saturday, and Wilder wants the senior players to take on added responsibility while the squad is stretched.
He said: “People have to stand up and be counted.
“(Dave) Kitson did that at Cheltenham, (Andy) Whing and Mullins did that, Raynes did that, they are the reasons we brought these guys in.
“If we do have situations like have happened this week they roll their sleeves up and go that extra little bit.”
There is one positive on the fitness front, with Rigg expected to return in training today.
The winger suffered a minor tear in a hamstring in the 3-1 win at Torquay United last month.
It was initially predicted it would keep him on the sidelines for eight weeks, but the recovery is ahead of schedule.
The 25-year-old will be closely monitored, but Wilder has not ruled out including him in the squad to face leaders Chesterfield on Saturday – five weeks after picking up the injury.
He said: “Hopefully there might be some good news regarding Sean Rigg.
“If he trains all week, he’ll be involved on Saturday.”