The 56-year-old spent part of the weekend being given oxygen in intensive care and he remains in hospital.
"It was scary news and it did affect me," Shrewsbury assistant manager Wilbraham said.
"It's been a crazy time and it was quite worrying. But Sunday and Monday has been non-stop improvement.
"He's on the mend so it's definitely good signs, it's a relief to everyone.
"I've spoken to him in the last couple of days and I can tell he's getting better.
"His voice is getting better and he's starting to crack a couple of jokes. He's told me to tell the boys he'll be watching (the Southampton game) from his hospital bed, so they'd better be at it."