The England international fell down the pecking order for both club and country last term, finding himself as more of a squad option than first-choice pick under Jose Mourinho.
Following United's victory over Ajax in the Europa League final in May, Rooney claimed that he had made a decision over his next career step, leading to strong suggestions that he would move on this summer.
A month on his short-term future still remains unclear, which former teammate Neville believes could potentially 'clog up' the Red Devils' pre-season preparations due to the constant speculation.
"You don't want to create voids for speculation around such big players," BBC Sport quotes him as saying. "I am surprised it has not been dealt with.
"You don't want that speculation to hang over a pre-season because every single press conference and media session will be clogged up with the issue of whether he is staying or going."
A report in the British press last week suggested that Rooney, into the final 12 months of his United contract, is struggling to find any interested suitors.