Rooney will miss the entire group stage of the competition after he was handed a three-match ban by UEFA this week following his dismissal from England's 2-2 draw with Montenegro earlier in the month.
However, Ferguson has insisted that Welbeck will be prepared to step in for the Three Lions, amid fears that England may not progress to the second round.
"Wayne is very disappointed at UEFA's decision," he said.
"There are no guarantees England will qualify from the group. With their record in championships, a three-match ban for Wayne could mean he'll miss the whole thing.
"I think he [Welbeck] is almost certain to get his chance now. He's ready for England."
Welbeck made his senior debut for England earlier this year in a friendly against Ghana.