Robinson described his side's defending as "shambolic" as the Saddlers recorded their first away victory for three months at stadium:mk, winning 4-2.
He said that Mathias Doumbe, Antony Kay, captain Dean Lewington and Adam Chicksen would not play together in defence again. But with Gary MacKenzie (hip) still out, Robinson does not have many options available.
Midfielders Stephen Gleeson (broken foot) and Luke Chadwick (knee ligament damage) are also out for several weeks, while on-loan Chelsea striker Patrick Bamford looks set to rejoin them on the sidelines.
Bamford returned from a hamstring injury as a half-time substitute against Walsall but a tackle by Saddlers skipper Andy Butler saw the teenager doubled-up in agony on the pitch, forcing him down the tunnel before the end of the game.
Robinson said: "I thought the tackle on him was bordering on assault. He kicked him, didn't hit him then lashed out again. It looked like he tried to do him, tried to hurt him. I like firm, in-your-face tackles, but not when someone goes to hurt someone.
"To lose Patrick is a big thing for us. But when you add him to Gary MacKenzie, Stephen Gleeson and Luke Chadwick, we're going to be depleted. At this level, it's so hard to replace them."
Charlie MacDonald and Alan Smith were joined on the bench against Walsall by 16-year-old Dele Ali, 19-year-old Zeli Ismail and Ibra Sekajja, 20, and Robinson may have to include more youngsters among his substitutes on Saturday against Coventry, who are unbeaten in nine matches in all competitions.