Vivell's position remains termed 'interim' director of recruitment, but he will step up now with only three weeks to run before the opening of the winter transfer window.
With Ashworth dumped, there are no plans to make an immediate appointment as a replacement.
Instead, United will count on Vivell and technical director Jason Wilcox to manage the January market and potentially the summer transfer window also.
Both men were answering to Ashworth in the chain of command. However, they will now take on a greater responsibility over the coming months.
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