The 20-year-old broke a bone while taking part in the 3-2 home defeat against Derby County on 11th March.
He had to undergo surgery and is expected to be sidelined for the remainder of the season, in what is a bitter blow to his hopes of a strong finish to the campaign.
Manning, while sympathising with Bate, revealed how the Leeds United-contracted player reacted to the news.
Though Bate had the desire to keep on playing in spite of having picked up the injury, the decision-makers opted against taking the risk, Manning revealed.
“It’s unfortunate but unavoidable. The nature of the injury just means we can’t risk him playing right now”, Manning was quoted as saying by the BBC.
“He wanted to play on but we can’t delay it or it could lead to long-term issues and that is too great a risk.
“So he is going to have to sit the matches out for the foreseeable future.”
The 37-year-old further took time to tip the young 20-year-old to have a bright future ahead of him.
“Lewis is gutted but he is a very talented player and has a very bright future ahead of him.
“Oxford fans have seen that this season, and like us will be wishing him a speedy recovery.”
Bate has featured in 28 of Oxford United’s 37 league games making four goal contributions.
A product of Chelsea’s youth academy, Bate has managed four senior appearances for Leeds United.