Washington(CNN) Ben Carson explained last week's major staff shakeup Sunday by saying he's now "in a different ballgame" and the campaign leadership he had in place was unable to execute its own plans.
The retired pediatric brain surgeon and Republican presidential candidate discussed the departure of his chief of staff, communications director and policy director on ABC's "This Week."
"We have had very good people that had very good ideas and no one predicted that we would even be in the hunt," Carson told host Martha Raddatz. "It really is quite spectacular what we were able to do. But the fact of the matter is now we're in a different ballgame and we need the ability to execute and not just have good ideas."
Carson said that the "very substantial changes" he wanted to make were a problem for departed campaign manager Barry Bennett -- who Carson said "decided that he could not live with those changes and that's OK."
"It doesn't diminish anything that he's done. I think he's done a fantastic job," Carson said.
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Bennett told Time Magazine that he was furious about Carson business manager Armstrong Williams' role the operation, arranging interviews that the campaign hadn't been made aware of.
He pointed to December 23 interviews in which Carson previewed a staff shakeup -- without informing his campaign first. Later that day, Carson walked back his own comments.
Bennett said it would take "some psychologists" to figure out why Williams has such influence with Carson.
Carson, meanwhile, was critical of Williams himself.
"He's made some bad judgments. There's no question about it," Carson said. "But, you know, he's a friend. I think he's a valuable individual."
"We can't have people working at cross purposes, and that's one of the things that has to be fixed and is being fixed and is fixed, in fact, at this point," Carson said.