POTUS wouldn't be choosing him if he wasn't on the same team. There would be absolutely no chances taken here.
Mr. Barr has criticized aspects of the Russia investigation, including suggesting that the special counsel, Robert S. Mueller III, hired too many prosecutors who had donated to Democratic campaigns. Mr. Barr has also defended Mr. Trump’s calls for a new criminal investigation into his defeated 2016 opponent, Hillary Clinton, including over a uranium mining deal the Obama administration approved when she was secretary of state.
“There is nothing inherently wrong about a president calling for an investigation,” Mr. Barr told The New York Times last year. “Although an investigation shouldn’t be launched just because a president wants it, the ultimate question is whether the matter warrants investigation.”
Mr. Barr added then that he saw more basis for investigating the uranium deal than any supposed conspiracy between Mr. Trump’s associates and Russia. “To the extent it is not pursuing these matters, the department is abdicating its responsibility,” he said.
https://www.nytimes.com/2018/12/06/us/politics/william-barr-attorney-general-trump.html