I think he probably has followed through," Ferguson told Sky Sports.
"He's caught the boy, not high, but just above the ankle and I think that in the present climate the referee is probably correct."
United moved into the quarter finals of the competition with a 2-0 win at Oakwell courtesy of goals from Danny Wellbeck and Michael Owen but after the sending off of Neville they had to withstand some excessive pressure from the Championship side.
"It was a cup tie and Barnsley have worked very hard," Fergie added.
"They put a lot of effort into the game and they had one or two chances after we went down to ten men.
"I think at the end of the day we've just about got through and probably deserved to get through.
"When you're playing away from home in a cup tie it's a different experience than playing in Old Trafford.
"Last year when we won the cup we got a lot of home draws until the semi-finals when we had an away game with Derby County of course."